Oh you're right.. I forgot TBC is required for ally shaman. And wotlk for DKs.. In that case a lot of people have enjoyed multi- Druid groups. But if you're mainly looking for an army of 60s before you level beyond it doesn't really matter all that much what you start with. Just be aware that you may start bleeding from your ears sometime during your 300th trip through scholomance, so filling all your slots with 60s may start to seem less attractive down the road.