Titan Collossus Boss Hit Box vanishing

Bug Report ID: #2717694837

I tried the boss on my necro now around 10 times, it normally goes around 1/4 of HP into a mode were neither I nor my minions are able to target it anymore. Even trying to prolif the damage through boss minions on to him with contagion/ED combo doesn't work anymore.

I am using

- skeleton warrior from sceptre with elemental army and last grasp
- ED with persistence and minion pact
- Contagion
- enfeeble
- unearth

Once he lost his hit box at 3/4 life. I cannot progress with that kind of problem. Tried to keep fighting but gave up around 5 mins in and just let myself be killed there.

Same issue. how can i up this post?!!