Any healer, any tank and any 3 ranged DPS. Composition really doesn't matter in 5 mans, they're all faceroll. If you're planning on doing LFR/raiding, I'd go with a Druid tank and Priest, Druid or Shaman healer. This way you can dual spec both your tank and healer as ranged DPS when you PUG. Playing 5 of the same role is a lot less problematic than trying to tank and/or heal while controlling DPS at raid level.