Zelina and Zolin

Zolin won't trigger the lasers or blood bubble thing until he has lost health. If you can contain your damage just to Zelina until she's dead, you can dance around all day and not worry about some of the worst attacks from Zolin.

Currently my character is a Lich Witch

level 69
spirit 431
skeletal warrior x3
skeletal sniper x1
skeletal arsonist x1
skeletal frost x1
skeletal reaver x2
skeletal storm x1
skeletal brute x2
Ravenous Swarm
Unearth
Flame Wall

And i find it impossible to beat these two bosses no matter how hard i try or how i reconfigure my minions - besides, the fight arena is too small and way to many things happening at the same time.

its not fun
its not engaging
its not challenging 
its just irritating 

I must've got lucky -I beat them on the 1st try last night but they were very difficult. Im playing a Lich as well (68), I have 3.4k es /1300 life, used 5 arsonist, 2 warriors, unearth, flame wall, Srs, frost bomb, pain offering, and I have blasphemy with Elemental weakness. I almost had one dead then it leeched back to total full health and it took me a good 10 minutes it seemed like, dodge rolling and staying as far away as I could. Its by far the worst boss encounter and needs adjustments...

My face to fist-style monke rode the strugglebus for a good chunk of time here even after I built hard into corrupted blood immunity and hindering enemy regen. But then again, my build has a lot of "questionable" choices that I do reign in to be more "meta" if I feel I've really hit a wall that can't be overcome otherwise.
I think I heard a lot of those reduced/no enemy regen mechanics didn't work on the leech/this fight. Idk if that was true, I just know I beat em (eventually). Was I able to block their regen? Was it my improved defenses against bleed/corrupted blood? Bit of columns A and B? It sure af wasn't my elemental/chaos res, I can tell you that.

This campaign, the fight that bothered me the most was probably the Siren fight because she was constantly going immune to dmg. I struggled in a few places, but that one was maybe the one where I sat there and thought, "this is not fun." They adjusted the Zelina+Zolin fight in last night's patch but IDK how much that will effect most people's struggles here. Hopefully it's not a busted fight because I kinda like having the threat of getting my ass kicked in campaign. But I can understand if it's currently still a bit overtuned and needs to be reigned in a bit.

[the next day]

After 20+ attempts in total and 15min+ in the last try - i finally managed to beat them in the most dumb way possible..

I just kept running circles around the room and dodging their attacks while my minions would do whatever they wanted, i used all my health flask but stayed alive long enough to see them kill zolina - only after that i could finally engage in combat and kill zelin

However, after i got the mission completed alert, he still keep fighting and doing damage; i had to lure him to one side of the room so i could talk to the hooded one and actually finalize the mission.

Maybe there are still some bugs left in this fight; i hope they address it because up to this point the game provided and amazing experience and all my previous deaths were my fault.

I've noticed some bosses have insane regen or defences, and then after a while I just stop looking at their health bar and concentrate on dodging and weaving and they eventually die. I noticed a few bosses that I thought near impossible, would eventually start to break down after a while. There was this boss in the halls of the dead that would regen faster that I could damage it, and it made me start a new character. It was still regening way too fast, but then it started to regen a little slower, and eventually it stopped having regen and died. I would not have figured it out unless I persevered, I assumed the regen was a bug or that I just had the crappiest builds.