A bold statement, I know, but one I stand behind despite a deep appreciation for Sorcerers as a class. Let's assess each skill within Daedric Summoning individually:
Summon Storm Atronach:
This was Daedric Summoning's bread-and-butter skill until it was nerfed in 1.3. The thing that made this Ultimate distinct from, say, Standard, Nova, and Veil was its ability to taunt targets. I presumed the ability to taunt was also the reason Storm Atronach had a health pool and could be destroyed. Its taunt was unique and made it a strong ultimate choice.
Now that the taunt is gone, this Ultimate is simply an inferior version of every other class' marquise ultimate. Give me Standard, Nova, or Veil over post-1.3 Storm Atronach any day.
Summon Familiar:
ESO should not have attempted to implement pets. As a veteran MMO player, I am familiar with pet-balancing issues. Unfortunately, without extremely sophisticated player controls, pets are always OP or UP.
Now, ESO pets aren't totally UP--but they are totally underwhelming. They really don't promote any kind of interesting play style. That's pets at their best. At their worst they cannibalize important heals in group content. There's a reason why VR players never used pets until Summon Volatile Familiar became bugged.
Daedric Curse:
IMO the best single ability in this line, though it is very situational. I see this skill as being built for PvP where Sorcerers use it in tandem with Mage's Fury (4 second delay) to stack and time burst damage on an opponent. But it's lackluster in PvE because there is a delay and because only 1 can be applied at a time.
That's great that it feels like a PvP-oriented skill. But the fact that the best ability in the line (best IMO, of course) is not particularly suited for PvE strikes me as problematic.
Summon Twilight:
See above at Summon Familiar.
Bound Armor:
An interesting and pretty excellent skill--but wholly outclassed by Storm Armor. Why--WHY--does Bound Armor need to operate as a costume?
I can see magicka-starved builds using it in place of Storm Armor. Overall not a bad skill to have, but the graphics of it absolutely suck.
Conjure Ward:
For a first-hand lesson in frustration just compare this to DK's Obsidian Shield. Obsidian Shield creates a better damage shield for the same amount of time and also applies to Allies. There's nothing more to say.
Passives:
The only passive worth mentioning (because all the other passives apply to pets, and as I've posited above, pets are garbage) is Power Stone. It is a beast of a passive. But 1 passive out of 4 is hardly impressive.
Recommendation:
1) Scrap this skill tree. Make it a World Skill available to all players so all players can effectively ignore everything but Power Stone. Give Sorcs a newly-designed skill tree.
Or -
2) Remove ALL pet functionality. Rework Summon Storm Atronach into Summon Lightning Rod, a Sorcerer equivalent of Standard of Might. Remove Familiar and Twilight, replace with skills that provide some group utility.