It seems Korvaak death triggers the Eldritch nemesis spawning, makes me wonder if I prolong the Korvaak 2nd phase where he spawns many eldritch mobs, will it enable us to face Korvaak and Kaisan at the same time? Same question with Theodin+Aleksander, or Loghorrean with Big Benn and Grava.
I had a wild Kaisan in East Marsh during a celestial totem clear. At the same time I had a Kuba because of a random groble kill. I wonder if 2 nemeses such as these is worse than a nemesis plus an act boss. I never found out how bad Kuba plus Kaisan was… I exited the game because on HC. Was too paranoid to find out if they would fight each other.