You can get all sorts of players on pug. I just adapt. First pull already tells me how tough is the tank. I'll focus heal when tank is undergeared or pulling too much, dps more when tank handles really well. I've also seen tanks does silly things like undergeared tank pulling 2 or more groups. Healing just cannot keep up and sometimes no CDs on lower levels. I've experienced 2 wipes due to undergeared tank pulling 2 or more groups again not long ago.

I've also tanked. Pulling 2nd group depends on how often the healer keeps my HP full. I'll do 2nd group only when last mob remains on current group if I feel healing is questionable. I've seen DPS focused "healers".