I used to play on a pve-c server and players from different clans could run around together and fight bosses or whatever and thralls would not attack unless you jumped directly in front of them during fight.
I have a pve-c server now with similar settings and whenever we even get close to one another our thralls go crazy with bloodlust and start attacking everyone in sight so not able to hang out together.
they behave the same way on officials now , mostly if you set them on attack everything in their engagment behaviour tactics . the best would be to set them to guard me or do nothing , and order them to attack with the command , at least when you want to fight dungeons ect together !