Some replies I got from a faster forum:
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I had the same thought process and ended up going straight up the middle and making thralls. I was full of regret.
1) You can only Thrall "man and mer". Severely limits your options -- no bears, no Deathlords, no trolls...
2) For some reason, Thralls lose about 100 IQ points when raised -- that uber-bandit forgets how to use his sword and shield and dies about 5 seconds into a brawl. Think about how fragile Lydia can be, and then cut that lifespan by about 90%.
3) Thralled "civilians" report your crimes. Awesome.
4) Dremora Lords pwn any sort of thrall you can make, Dead or Elemental. Its frustrating.
5) Ice Thralls will block doorways/small passages constantly.
6) Flame Thralls are not so bad, but will die every "major" fight. Just too fragile.
7) Thrall Spells require two hands and have a long cast time. Not a biggie, but it means you can't just have them at the ready in case a thrall goes down.
8) As far as I can tell, none of the Conjuration Perks affect Dremora Lords except for the one "half-mana" perk. Easily offset by some Fortify Conjuration enchants, or a large mana pool. You can cast the best Conjuration spell there is and spend no perks.
Summary:
I was really upset at how underwhelming dead thralls are, considering how much effort it takes to get the spell.

Then again, being able to have 2 dremora lords running around is pretty awesome, but is in the realm of overpowered and doesn't leave much for you to do but watch the carnage.
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Well for me, I only choose one side or the other. You can only have 2 summons/atronachs/thralls at a time, so going up one tree just so you can have both is a waste (I know, I have tested this).
I am trying to do something similar to you. Making a sword and shield warrior who is also a necromancer to have a posse of awesomeness.
I would say pick one side, either necromancy or atronachs, in your case you would be using dead thralls which is fun.
I agree that the elemental branch produces better results IMO. You still get the dead thrall and if you need to use elementals, they're more powerful and last two minutes.
I personally prefer using the recastable elementals instead of permanent ones since that allows me to place them where I want as a battle begins.
I haven't played with Dead Thrall too much yet. Summoning two Dremora Lords and watching them annihilate everything in their path hasn't stopped being fun to witness. I kinda want to find a conjurer to keep as a Dead Thrall, then bring a conjurer companion, then use my second pet summon to conjur an elemental as well.
When your dead thrall dies, you can just bring it back to life anyway, so the plus 100 hps isn't really a big deal. Add the fact that you can just place +HP gear on the corpse before you summon it and the perk loses even more value.
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TC, I thought of this too. And I will tell you that Dead Thrall can outkill any dremora lord you have, let me explain.
You can give you dead thrall a legendary smithed daedric weapon with absorb health on it, this is incredibly good.
You can enchant all their armor that they wear, ONLY if it comes off of their body. Smith this stuff, they will be bulletproof.
You wouldn't want to raise a civilian anyways, because they all svck. Named bandits, bandit marauders, master conjurers/necromancers are good. Master conjurers use atronach spells and necromancers will raise the dead.
Your dead thralls can use staves. I gave mine the Wabbajack once, that get's pretty out of hand though. Give them a Summon revenant staff or storm atronach if they are melee thralls.
That +100 health boost is more than you think. Try summoning an atronach and killing it, with and with out the perk for them. Do the same for a thrall, you'll notice that they seem to get the same exact health boost. Duration can affect dremora lord cost, but you can just repeatedly summon them with out cost.
Archer/daedric bow equipped dead thralls are extremely powerful. Dremora lords go out of style. If you want a video proof of how good they are, let me know and I will make one. Will take me a couple hours though to get a hold of my camera.