With my Shaman, i rape Mages/Druids/Rogues/Warlocks. I can still Warriors, but it's harder because of their huge HP. I can take Priests, it just depends on how the battle starts, generally i Tremor Totem, then Earth Shock (If they are casting something, ie - Mana Burn, otherwise i'll wait till they start casting), then Healing Steam totem and hope Windfury procs alot
Priests shouldn't be too hard to kill, any casters generally get pwned by Shamans. Harder for me against non-casters.
My Shaman is only 30 so i don't have my Air Totem (For Grounding Totem) yet.