Nope. In terms of Damage, Dremora Lords can out-damage even Draugr Deathlords. Furthermore, enemies that are weak to fire get completely obliterated by their fire enchanted Daedric Greatswords. They are fast and relentless.
Most durable? Potent Frost Atronachs. But they have low damage.
Wrathmen: Good durability, good damage, slow movement.
Storm Atronachs/Seekers: decent durability, excellent at range. Storm Atronachs can also hold their own in melee combat.
Best overall: Dremora Lord. Their one weakness is magic though. Their Daedric armor gives them protection from heavy-hitters, but arch-mages will tear through them. However, in closed interiors, Dremora Lords will destroy the arch-wizard if they can close the distance fast enough.
Seekers and Storm Atronachs are better against mages. Especially if you are melee, they give great support from afar while you rush the enemy mage yourself.
Hevnoraaks right, so long as we exclude Karstaag.
I excluded him since he's a three-time-only summon. But yeah, no one can beat Karstaag. Not even the Ebony Warrior.
I've taken to using Wrathmen almost exclusively instead of Dremora Lords. Dremora Lords are a little *too* good at what they do, and I like my character to be a bit more... necessary to a fight than simply acting as the doorway for better fighters.
Also, Wrathmen are blissfully silent. The Dremora Lord's verbal cues get old real quick.
How about Arniel Gane's shade? Does that count?
I figured as much, just though he deserved an honorable mention
Alteration?
Paralyze is good for a warrior, as is Ash Shell. The various -flesh spells are good for hitting the Armor Cap early on. Most of the rest of Alteration is utility type stuff. Useful no matter what build you're running. Detect Life, Water Breathing, TK for reaching tall shelves.
What about Ash Guardian? I've seen those things tear through dragons like fire through paper.
Dremora Lords are the sole reason that conjuration is overpowered. With the twin souls perk, you bring out 2 of those guys, and rule all of Skyrim.
Just love the Dremora lord twins, they put a stop to most problems!
Difficulty doesn't matter. Besides, they have 345HPs, which isn't that low.