IMO, you should always have one class that can rez per team, if only to minimize downtime after a single toon dies. On my warlock team I make sure to soulstone the priest, and if I'm gonna wipe, I move the priest to a safe spot so I can rez the team and start again. That way I have 4 soulstones, all for the priest, and can wipe every 10 mins and not have to do a corpse run. Plus, just being able to heal the pets can prevent the wipes from happening in the first place.

One corpse run to places like Wailing Caverns or Blackrock Depths will make you hate not having a char that can rez.