2 players party - 6 times boss HP on death

Hello there,
me and my friend find out that when you die in 2 players party, then after spawning at checkpoint, boss HP is for 6 players group. Found out on the Chimera boss, act 2 last boss or Ultimatum boss Blackjaw. Example:
- first pull in zone, we did 35k dmg and boss had 50% HP
- second pull after death, we did 120k dmg and boss had 50% HP