Main boss in 4th map (Sanctuary of Secrets):
Sometimes it just 1hit ANY of 4 players (even warriors) and only then it shows animation (of his breathe) and red zone

Main boss in 2nd map (The Newland Star):
It has something similar, he shows red zone and after 0,1 sec it already has killed (or almost killed) one of players, I don't even have time for use pet AA, not telling about warriors/mage to charge their horn/shield and use it