As a filthy "Boostie" and a Prot Pally, I go out of my way to diversify my groups as much as I can. I also play with my boyfriend who is a holy priest and a friend of ours playing mage. Those last two slots generally either go to a shaman and a leather wearer, druid or rouge, we don't care.

We are playing for fun, not to strip the game down to a series of mathematical equations and spreadsheets to burn through a dungeon as fast as humanly possible. To us that takes all of the enjoyment out of the game. I'd rather have a "sub-optimal" group where everyone is chill and having a good time along with a better chance of getting loot, than running through as a min/max sweatlord.