Attacks of new bosses kills couple of minutes before attack even visually loads

I tried to fight new Incarnation bosses and ALL THE TIME i got oneshot out of nowhere. And only after couple of minutes staying on death screen - visual effects load and i can see what killed me

Any advice, how to deal with that? Cause i will not play new bosses (Sadly) until this is fixed or dealt with)

Other bosses are okay-ish, but in last few patches - i still sometimes get oneshot out of nowhere by skill that was not visually loaded