Yeah, that was just a horrible situation to be in, OP. If anything, the main thing that irks me is a WHM spamming Medica throughout a dungeon constantly drawing aggro to themselves.

A) It makes the healer in danger of dying.
B) It makes it MUCH more difficult for the tank to draw Aggro(unless Provoke is up).
C) It isn't smooth.

Usually whenever I start, I check their levels. If they're synced(or have a 60 in another class and are unsynced) then I expect them to do good at their job unless they just don't have a great overall idea of it. Only then do I give advice.