5 man
tank: paladin, druid. warrior has a hard time building aggro on packs. it needs cc from other classes to work well.
dps: whatever has cc. casters are not so gear dependant, so they do the most damage. mage and warlock best aoe.
heal: doesn't really matter.
raid:
tank: warr main tank, pala, druid off tank
dps: every raid will want at least dps shaman (spec doesn't matter much), spriest and mage. you never go wrong with them
heal: hpala best heal for main tank, but all the others work
T6 best dps: rogue (highest potential), hunter, warlock, warrior
As mentioned above, you won't find that many rogues. In fact, the server is flooded by mages, hunters and warlocks. Whenever I'm LFM, that's what I get all the time.

