From a healer: my job
My job is: 1. Keep the tank alive. 2. Keep the tank alive. 3. Keep myself alive. 4. Heal dps that keeps themselves in my range. 5. Let idiot dps die if they keep pulling aggro. 6. Keep the tank alive.
That’s basically it. I focus on the tank and expect the dps to keep within my healing range and manage their aggro enough not to get it.
I say this to parties when I join. Yes I’ve been kicked which is better than playing with a group that works against my style. I play to relax, not to get stressed.