2x pallies vs 2x shammies in 3x warrior team

[Apatheist]

You can't look at things in a vacuum like this though. You will spend a considerable amount of time in world PvP defending yourself against gankers even if you have no intention of actively seeking PvP.

Also consider whether you enjoy playing each of the classes in your team individually as you'll often only be able to raid on a single character.

Either of the groups will be able to clear dungeons fine. At some point you have to consider what you will actually enjoy playing.