Some of these awful little tanks (I speak as 50 PLD and 50 MRD) need an instance that teaches them how to hold aoe hate. I've run into several paladins that don't flash at all...ever. Everyone else hate some amount of hate on the entire pack (usually trying to get it off the whm) and the tank literally has none.
You can't make players better who refuse to be better, but some people are just dumb and would benefit.
It is true that a sucky tank is more evident than a sucky dps but the group also suffers more due to a sucky tank.
These guys are such self-important plate-armored divas that they take offense if you try to guide them. I've tried being as nice as I can be and sugar-coating things like "No offense, but please overpower more." (Usually more than 0 times), but they either don't respond or get all uppity.
And yeah, I've made a similar thread before.
Before they can queue for dungeons, they need to learn to keep things off some npc healer that won't heal itself but will heal the tank. If healer dies, fail. Can even be nice and put a bard npc in there too with ballad up so they don't run out of mp. A paeon bard for marauders.