In general U51 was a big boost for casters. I think sorc and wizard did relatively better than warlock, but warlock gains were significant.
As an example on my bladeforged SE/TS DC build, my single-target dps more than doubled compared to pre-U51:
https://docs.google.com/spreadsheets...it?usp=sharing
This was the single biggest weakness of soloing with warlock by a large margin. With lgs debuffs, warlock debuffs and warlock vulnerability it brings dps the numbers can be boosted significantly but will never match a properly built melee.
ES/TS blasting builds made significant gains.
My initial thoughts/testing indicate that Draconic as a main tree is going to be best with exalted angel and primal avatar as secondary trees for mass cure moderate and cocoon.
In addition, you can go more tanky with draconic, exalted angel, unyielding sentinel or draconic, unyielding sentinel, primal avatar.
Even with the loss of empyrean magic fire still makes alot of sense since you get crit chance boost and spellpower, plus immunity stripping with tiefling. I would almost certainly take arcane tempest rather than wail of the banshee on the blasting build. Ruin, Greater Ruin and Arcane pulse also make sense and synergizes well with arcane tempest and tentacles which use force.
Cold is also quite good as absolute zero is arguably the best pact ability and niac's biting cold is boosted by draconic. I will update the builds, but I have alot of testing to do first and I want to wait a few weeks until some of the bugs are fixed and possibly a few numbers adjusted. On my bladeforged carceri warlock I am currently testing out draconic main, magus, pa and it's working really well an synergistic.
Fey pact has synergies with scion of the feywild and fatesinger sonic vulnerability and ironically highest dc potential, but I am just not seeing the dps there unless you go melee as an arcane warrior. The turn tide party buff is quite a nice side benefit. It will take some testing and finesse to make fey pact with fatesinger work, but the potential is definitely there.
Even on my bladeforged I am looking at ES/TS instead of SE/TS as an option since blasting is so much better and the aura and vortex compliment each other so well.
On a side note for folks that solo, you should definitely take advantage of the free coupon code to make a buffing bard sidekick. If you can throw a small amount of money at the account it will save you from needing to grind points to buy xpacs.