Two Dremora Lords can take down almost anything. Ancient Dragons are the only thing they can't trash, and certain caster NPCs like arch cryomancers. They aren't very resistant to magic or breath attacks, they don't have a ton of health either they just deal a ton of damage relative to other summons. They really excel vs. melee, I'd say Draugr Deathlord vs. Dremora Lord can go either way, depends on weapon of the Draugr as well as which one staggers more, blocks more successfully, etc. I'm not sure why some people are reporting they get owned by them, since the Dremora scales for difficulty it can't be that.
I just tested pitting a single Dremora Lord vs. a Deathlord with an ebony sword and these were the results -
1. Deathlord
2. Deathlord
3. Dremora Lord
4. Dremora Lord
5. Deathlord
6. Dremora Lord
7. Dremora Lord
8. Dremora Lord
9. Deathlord
10. Dremora Lord
Dremora Lord wins 6/10, so I think a pair of them would beat a Deathlord almost every time. A Deathlord with a 2 handed weapon might fare better or worse, but I doubt it'd make a big difference. Dremora Lords stagger with their power attacks quite often, and when watching them face Deathlords I could usually predict the winner based on that. A dremora lord that gets a few staggers early on will generally win.
Thanks for testing it, they seem pretty evenly matched ha.
This is useful, but remember that if you summon 2 dremora lord vs 3 draugr deathlords, regardless if they can kill the deathlord, it's less heat on you. On master thats what you need to be honest, as those things hit like a truck (especially the 2h ones).
That's why I use potent storm thralls against dragons, they have upgraded health compared to atronachs, and they have a decent ranged attack. I do like to fight my own battles most of the time though ha.