So far I have tried to help out people as much as possible. I haven't been anything other than a tank in the instances, and I consider myself somewhat capable, so I don't know what it's like to run with one that's terrible. I have come across bad healers and bad DPS though, trying like hell to pull aggro off of me for some reason. The main thing I always try to get across is try to target what I'm targeting. With healers I would stress not to waste time casting stone, because the damage you are doing in the end is usually meaningless imo. That is not always the case, but I will give an example of a bad healer. I was running whatever the last instance is, the lvl 32 one, and we wiped at the first boss. My MRD has at 1400 hp going into that fight, and the healer would let me get down to 400-500 hp before he would even start casting any heals, and instead would spend his time casting stone. Then he would struggle like crazy trying to get me back up. We wiped pretty hard. How do you even get that far as a healer without knowing how to heal in an instance? I figure somebody would have given him a heads up at some point, like hey, quit casting stone and friggin heal the tank.
Whatever though, most of the other healers I have come across know their role, so it's not a big deal.