if your going 4 man, i'd suggest rogue tank, paladin main healer/off-tank, shaman off-healer and any other dps class, most likely rogue, but go hunter if you can get [ITEM]Feathered Arrow[/ITEM]
Have rogue pull aggro and start attacking, with paladin healing when needed, rogue use bandages+lifeblood as often as possible, paladin also builds a small amount of threat, once you think rogue has enough aggro, rogue/hunter start to dps, and paladin keep healing when needed, in emergencies, shaman heals, since their heals are better, so they have more aggro, this is why paladin is healing in most cases, because they can wear mail, and are therefore better tanks, but shamans have nice high heals so are good when needed, shaman can also use lightning bolt/auto-attacks whilst not healing, if paladin does pull aggro, they should keep healing themselves to try and hold aggro, or at least until rogue gets aggro back, and keep doing this, using bandages+lifeblood as often as possible(they heal alot so cause alot of aggro, rogue should use on himself) this should work for just about encounter