Really simple! Keep stoneskin on all members of the party as best you can, only use Regen on the tank during boss fights(not trash pulls.... it's just dumb to cast a 21 second HoT that generates a ton of threat and risk it ticking during an initial pull)(except for the demon wall in AK.... regen and medica 2 means you can just jump around the whole fight and cast holy if you are good enough), and only use regen on the party if you know there is about to be a big group attack to help with spike dmg.... I rarely pull aggro during runs unless it is a terribad tank... and even then, I just heal tank if the real tank blows donkey dongs...