While the Wolcen devs goof off, I, and others I'm sure, have found a solid workaround for the Heimlock phase 2-3 bugs.

I ran the encounter over 100 times to isolate the cause of the transformation bug as an ailment sorcerer. I found that there were a couple times I could break the boss with toxic DoTs or DoT damage in general, but the overwhelming culprit is Aether damage .

Change your skills and weapons to NOT deal Aether damage.

I was able to easily beat the encounter with a white pistol and a blue catalyst from the vendor once I stopped using Aether attacks. Lvl 42 on Normal difficulty.

I hope this helps all those afflicted by the game breaking bug and the sleepy devs. i think the wildly unexpected success of the game threw them into party mode and they are sleeping off some nasty zima hangovers.