Tips on beating Legendary Dragons?

Ok , so being as I actually don't know what your play style is I will suggest my theories / practices of taking on a fabled Legendary Dragon from 3 play styles being as the following:

1. Warrior Type - Heavy Armour 2h/1h & shield, bow offspec , restoration.
2. Mage Type - Cloth Armour , 2h Spell Casting ( Restoration , Destro and ALL other aspects of magic infused power skyrim allows. )
3. Assassin Type - Light Armour , Bow main , 2x1h daggers , illusion & conjuration magic.

So firstly I will presume being at level 79 you will have the best of the best in items or close as all tactics should work the same but some maybe more gear dependent than others & all of the following are from what I find the best ways from my own experience. Secondly I will also take into account you have potions upon your person for different situations & are currently wearing the Amulet that decreases shout time by 20% (Amulet of Talos). Lastly I will take into mind you have a companion of sorts ( I will just generalize the companion for opposite play-style for maximum damage output in situations )

So you're running along minding your own business as Dragonborn thinking about how cool it would be to Fus Ro Dah a goat off a mountain top or your wife that you've married because you love being a single hero ( slipping in Riften if you catch my driften - Bad pun I know ) and you hear the roar of a dragon , a big dragon you look up and find this huge beast throwing out Fire/Frost out of it's mouth ( Apply appropriate potion to what dragon actually is ) you then take a deep breath and take a run towards it's direction ready to slay the beast and take it's soul , scale & bones to store and never look at again!

Warrior:

Opener

Draw your weapons and Dragonrend the dragon. While he is dropping to the floor find yourself what I like to call a ' Nordic Advantage ' ( find yourself a set of trees , rocks anything that can shield you in the worst case scenario that can give you a fair battle advantage as well ) and use it purely as last resort while this is happening your companion is waiting for the dragon to land or firing arrows at it & becomes bait. ( I am sorry )

Fight Rotation

Now for the good stuff! Aim for it's left back leg or right back leg these are the points in which the breath / header ( 1 shot kill ) and tail can't hit you meaning a extended period of life aslong as you do as I say. NEVERSTAND STILL! like Ever... You're just going to allow the dragon to rotate and beat the souls of its dead brothers out of you always rotate / move with the leg you're on to keep at it's side for as long as you can. While this is happening you're currently beating it down with your weapon and repeating Dragonrend on cooldown ( as much as you can keep it on the floor ). Maintain the damage and good moverabiltiy and you will be ok and eventually it will die.

Worst Case Scenario

This will be pritty much the same thing to do with all classes ... you mess up the movement the dragon turns round what do you do? the dragon one shots your companion what do you do? you run of potions and have low stamina so you can't hit it as hard as you like what do you do? You've no magic left to heal yourself as offheals , what do you do? Ran out of arrows so you can't kite him into the Nordic Advantage what do you do? my answer is simple ... RUN DRAGONBORN RUN!

Mage:

Opener

Draw your spells (Lightning duelhand) and Dragonrend the dragon. While he is dropping to the floor find yourself what I like to call a ' Nordic Advantage ' ( find yourself a set of trees , rocks anything that can shield you in the worst case scenario that can give you a fair battle advantage as well ) and use it purely as last resort while this is happening your companion is waiting for the dragon to land or firing arrows at it & becomes bait. ( I am sorry )

Fight Rotation

Now for the good stuff! Aim for it's left back leg or right back leg these are the points in which the breath / header ( 1 shot kill ) and tail can't hit you meaning a extended period of life aslong as you do as I say. NEVERSTAND STILL! like Ever... You're just going to allow the dragon to rotate and beat the souls of its dead brothers out of you always rotate / move with the leg you're on to keep at it's side for as long as you can. While this is happening you're currently beating it down with your spells and repeating Dragonrend on cooldown ( as much as you can keep it on the floor ). Maintain the damage and good moverabiltiy and you will be ok and eventually it will die.

Worst Case Scenario

This will be pritty much the same thing to do with all classes ... you mess up the movement the dragon turns round what do you do? the dragon one shots your companion what do you do? you run of potions and have low stamina so you can't hit it as hard as you like what do you do? You've no magic left to heal yourself as offheals , what do you do? Ran out of arrows so you can't kite him into the Nordic Advantage what do you do? my answer is simple ... RUN DRAGONBORN RUN!

Assassin: ( This one is a tad different to the rest )

Opener

Draw your Bow and Dragonrend the dragon. While he is dropping to the floor find yourself what I like to call a ' Nordic Advantage ' ( find yourself a set of trees , rocks anything that can shield you in the worst case scenario that can give you a fair battle advantage as well ) and use it purely as last resort while this is happening your companion is waiting for the dragon to land or firing arrows at it & becomes bait. ( I am sorry )

Fight Rotation

You're a badass it's that simple , you stand toe to toe with anything and can outmatch anything at anything because well you're just simply that good ... a lousy dragon will not mess you. so you go in for the kill , kite him with your bow ( move around him and fire arrows ) do this for around 10 arrows at his leg , run away into the Nordic Advantage heal a little if you get caught and come back out rinse and repeat till he is dead he will be because well you're a bad ass.

Worst Case Scenario

This will be pritty much the same thing to do with all classes ... you mess up the movement the dragon turns round what do you do? the dragon one shots your companion what do you do? you run of potions and have low stamina so you can't hit it as hard as you like what do you do? You've no magic left to heal yourself as offheals , what do you do? Ran out of arrows so you can't kite him into the Nordic Advantage what do you do? my answer is simple ... RUN DRAGONBORN RUN!

EDIT:

If you find yourself needing more distractions natural human Skyrim instnct should kick in here , resto yourself & cast a spell to raise a minion.

Well since you're asking this type of question, I take it you're not much of a (hold as much health bottles as possible, and have the best armour type of guy). I don't have to tell you that Having higher armour is best against any dragon, but here are a few tips anyway:

1. How to avoid these dragons- well, normally you could hear dragons in the distance, you could watch the skies and scout out the best ruote in avoiding them. sometimes you'll be put against them in a battle though, if it isn't a quest to kill a dragon and have the dragonrend shout, use it. this will force the dragon to land somewhere which gives you some time to run for the hills and try to hide somewhere.

2. Tips on taking them out- No matter what class you prefer, it really would just depend on what combat skill you have leveled up most, and what weapons you prefer, If a bow might I make a suggestion on using poisons (some mana depleting and alteration potions don't work on dragons), if you do use the bow and are near something with a roof try sticking near it and coming out to shoot the dragon and hiding inside to keep your health regenerating. Or if you prefer the good ol' sword then try to get out in the open, somewhere without trees or mountain area, This will force the dragon to land where you can take them out, try getting behind them so you don't have to get eaten but once you've hit a couple of time try walking back a few paces as the legendary dragon have a devastating tail attack. as for mage...well you could try figuring out what breath the dragon uses and using the magic type that's oppisite to it's own, so if it's a fire breather, use frost and cold spells.

3. Keeping my horse and follower alive through the assault- Well...you know NPC's. they just love to attack anything they see threatening. All I can say is that unless you see the dragon and made them wait somewere safe to take out the dragon, they're just going to charge in blaze on' and get themselves killed most likely. Or you could see if casting a fear spell on them would work, or yet again, other healing or helping spells for the followers. As for your horse, it would have been best to avoid the assault if you could in the first place. horses tend to be weak in-game as you probably noticed yourself...

Just a useful tip: No matter what class you are, or what you think you would need on the road, it's always good carrying a few arrows, a bow and a sword that you find worthy, try not to let the Kg capacity get to you, if you need a weapon. bring it.

I have faced Legendary Dragons more than any other type by a long shot. The first thing (besides their 4k+ health) is their Drain Vitality shout (most often used attack). This will remove 7 health, magicka, and stamina from your character every second for 20 seconds regardless of difficulty level or magic resistance (not sure about spell absorb). There are a few ways to avoid it.

1. Given some range and the relatively slow airspeed of this shout, it is entirely possible to dodge it completely. At closer range, you may not find this an option.

2. Some kind of ward. It can be the low level lesser ward you get free from Tolfdir at the start of the College questline, something better, or the effect on Spellbreaker. Any of those will totally negate the effects of this shout.

3. Become Ethereal (1 word). If you have it, you can use it.

If you do get hit, the severity of the damage depends on your build. I think for most characters at this high a level a single hit won't be too bad, but a second one in a short time span could be potentially disastrous. If you have Equilibrium (Labyrinthian, College QL), it may prove useful. Note you cannot cast any spells with negative magicka, even if you have gear that makes spells otherwise free to cast.

If you have Dragonrend, use it liberally (cooldown is shorter than shout duration). Your next steps will vary depending on your character build.

1. Since all dragons have 150 points of magicka they use to power shouts, a mage would do well to summon a storm atronach (or 2) and charge up Lightning storm or dual cast Thunderbolt to start. Stormies over flamers due to higher hit chance and more damage per hit, frosties will get crushed in no time trying to melee. You can switch to DC icy spear or Incinerate (ignite can work well too) when you establish the breath type and go for the opposite (PC users can cheat a little to know this on approach by selecting the dragon in the console and typing getav fireresist or frostresist, but shock is still better when they are flying around). If you're a mage who uses alchemy and enchanting, popping a custom potion of fortify destruction can shorten the battle considerably (even faster if you use the related Shalidor's Insight scroll in an emergency like an attack on a city or town). Just whale on it when you can whether it's flying around, hovering in place, or forced to ground. Shouldn't take long.

2. A primarily melee warrior type will get to work once the dragon is on the ground. When you have Dragonrend, they tend to stay airborne unless you force the issue. If not, it's a toss-up whether they tease you from the air for a while or land by choice right away. Ranged weapons or spells are not a bad backup option. Anyway, once you get it on the ground you can approach however you like. I suggest alternating bashes and power attacks as 2H or sword and board (so you can maybe block most damage from bite attacks), or just dual wield power attacks for those so inclined (you are at risk for much more damage when a melee attack hits you even while armor capped, but you can lay on some pain pretty fast). Again, this shouldn't take too long. Your odds are pretty good.

3. Thirdly we have the primarily bow and/or dagger users. Atronach backups are nice if you have the option. Otherwise, wail on them with a bow from a distance when they hover or land (either by choice or by force). If you are into alchemy (and perhaps enchanting) you can pop a Fortify Marksman potion to speed things along. Probably not necessary, but can be quite beneficial when under attack in a city or town. If you are all about daggers, you might just wait until it's on the ground and run up to do a super mega ultra death combo (crouch into shadow warrior and combine a well-smithed dagger with assassins blade, shrouded gloves, a power attack, and savage strike in 1H). I don't know if dragon's fall for shadow warrior after they detect you (seems Draugr and vampires see through it), but you might land a one-hit kill even on legendary difficulty(depending on just how much of a smithing buff you have over base damage). Between a bow and a dagger, you can either take a while (safe) or get it over fast (pretty risky).

If you play a hybrid type character, you may be able to mix and match these strategies to your leisure, depending on your skillset and setting or situation. If you find a Legendary (or any other type) at a dragon lair, you may be able to get in a sneak attack to start for more damage (or get a one-hit kill with a dagger before the fight begins). There are a number of spots where you can take off a decent chunk of health with a sneaky bow attack (maybe a one-shot kill on lower difficulty with really good gear), but only one spot in Skyrim I know of where you can one-shot with a dagger (Dragontooth Crater in the Reach. Lots of good sneak gear or Shadowcloak of Nocturnal helps). There are 2 dragon nests on Solstheim where a dagger can one-shot the serpentine variety. They have less health (about 3500) but stronger elemental attacks (like an ancient dragon). Revered dragons are like that but weaker DV shout (5/sec) and worse elementals. A Legendary's DV shout is stronger than their elementals.

Finally, it's entirely doable to take out a legendary dragon on horseback (with a bow). I've done this a total of 2 times so far (both on this, my first legendary run) and it works quite well. Unless they sneak up on you to get in a DV shout, they are pretty easy to avoid otherwise and to circle strafe while hovering or on the ground. You don't even have to get off the horse to absorb its soul. That's pretty cool. You should dismount for looting, though. Happy Hunting.

If you dual wield, it is possible to "one-shot" a legendary on lower difficulties (given well smithed and/or enchanted swords and some good fortify onehanded gear) once your prey is grounded. For 1H/Block or 2H, you're facing at least a minor slugfest.

Regarding avoidance and keeping horses/followers alive. First, avoidance.

If you are traveling about, try to keep your distance from any known outdoor word walls. Sometimes dragons just show up. Sometimes they engage pretty much right away, so there isn't much you can do. Sometimes, they just fly around a bit and then fly off somewhere (often to a word wall, but not always).

As for keeping horses/followers alive? Let's start with horses.

If you intend to enter combat with a dragon in the near future (approaching an outdoor word wall location), dismount a fair distance away. The battle should take place closer to the word wall and your mount should be out of range. If you get ambushed on the road or in a field or something, keep on the move. Hopefully, you have a decent bow. If your character doesn't use real bows (not to say conjured bows aren't "decent", but you can't use them from horseback) then I'm not sure what to tell you. On to followers.

Ideally, a follower should be well equipped with enchanted armor that fits the way their class fights, and likely a well-smithed weapon or two as well if the follower in question isn't a pure mage. If they are a mage they should have plenty of extra magicka and regen enchanted on what they are wearing so they can keep slinging destruction spells and/or conjuring stuff like atronachs. Your combined might should take down the dragon fairly quickly. Hope this helps.