Depends on the content and the boss your fighting. For T5 (need lot more range dps on atleast hard bosses for mele) the perfect raid imo is:
Warrior tank, Druid tank/feral dps, Pala tank/retry, BM hunter, Enhancement shaman -->AP shout+5% mele crit+more extra damage from BM hunter+ wf/agi totem twist (if you have great dps tanks need a lot of aggro).
Enhancement shaman, arms warrior, and 3 spots for rogues, retry pala, fury warriors or maybe another feral for 5% crit mele for party (but for bosses like kael'thas or Leotheras you should have more hunters and less meles)
Elemental shaman, boomie, destro lock, destro lock, affli lock-->3%crit+hit(totem)+5%crit+improved curse of elements.
Elemental shaman, SP and 3 mages or 2 mages + 1 boomie-->3%crit+hit(totem)+mana regen+5%crit
Resto shaman, disc or hybrid disc/holy priest(improved divine spirit), holy priest, hpala, resto druid-->Mana tide totem+innervates or swap sp some times when needed.