So I also was suffering from this problem. I attempted the fight multiple times to no avail. It wasn't until I disabled show numbers and show critical numbers did the fight progress without issue.

I do have the same issue as well. Can´t finish the campaign.

Same happened to me. Tried not showing any numbers but it randomly switches from phase one to phase two and no damage can be dealt.

Same problem.
After he transforms, hemlock just stands around

Yep, I have same problem. cant get past this, as he just stand still at phase 2 and he does nothing. attacks doesnt damage him, no ads spawn, no nothing.. been restarting the game 4 times now. Still gets stuck every single time. Any idea what to do here?

Got the same issue, was able to get him going once in phase 2 but then in phase 3 same thing happens again.

The bug is still there for over 5 days now, can´t complete act 3

Same problem here.....phase 2 40/70%hp heimlock become invicible, doesnt moove

Just got the same bug, then i tried to change the difficulty on "Story mode", restart the game etc... and it work for me.
Maybe just got lucky, hope this will help

Same, i've tried it all. Changing settings, changing private, story mode, uninstalled the game and installed it. Changed every setting i can find, changed out every spell, tried leveling. Resetting passive tree and taking other nodes. Nothing works. I literally cant play finish the campaign due to this bugg, how was this not included in the patch today?!

Esimated tat i've done the fight up untill phase 2 about 20 times now..

same for me, I don't get, How can such a major issue not be fixed....

Just happened to me, first time doing this boss fight and yep, it bugged after Heimlock changed form.
He froze and wasn't receiving any damage. Will retry the fight later, hope this gets fixed soon : )

Me2..... 26 tries.... get the bug in p2 and p3 each time he "transforms" it could happen, so thinks like disable show numbers won't work... It is just luck... may be he bugged may be not....

love the game so far... but this is really hard.... Gamebraking bug against an Act Endboss and no reply if they mean to change it in time or we just need to hope that we don't get this bug...

Same problem here... nothing is happening and i can't do damage

This is just pathetic. After all the bugs we had to endure in this game and now i cant even finish the fucking campaign? Not even a reply from a dev when this absolutely game breaking bug will be fixed? The game is just straight up broken. It doesn't work. You are literally unable to complete this game. This bug already cost me 2 hours of re-installing and otherwise trying to find a fix. This bug put me over the edge and now i cannot even refund this game.

I reached act 3 and final boss 2 hours ago and managed to freeze the boss twice in every phase now... Still struggling. ffs.

Same problem.... Its so frustrating.

Same problem here. Tried it a dozen times. Boss freezes in phase2.
Tried it with a friend two times ... he creates the game. Same problem.
Then he tries to solo it and could complete the encounter without problems.
So it seems that it was me/my PC who was responsible for the bug in the coop game. Maybe some kind of hardware based bug?

Well, I managed to complete the Game now, too.

I closed all Windows applications, Browser, Discord, Spotify.
InGame Settings I switched from Windowed fullscreen to Fullscreen.
I changed all the graphic settings to Low!
Turned off all Motion Blur and Lens Flaires.

Then tried again .. it worked this time. Maybe by accident, maybe the settings changes made it.

Hope this also will help someone else.

I habe thw same bug