Yup. Tank/heals/DPS. Getting 2 more DPS for instances will be SUPER easy, and you guys have a lot of control in the group, meaning the groups will probably tend to go much smoother.
As for classes, you can pick that on your own. It can be the tried and true combo(Warrior, Priest, Mage) or it could be something completely out of the ordinary(Errrm, Druid, Druid, Druid?).
I re-rolled on a PvP server with two friends as well, and we eached just rolled the classes we wanted to play. My friends picked mage and rogue, and I picked a druid. For instances, we always have a ton of CC, and we always have either a tank or healer ready to go. Although I must warn you, if you go druid healer, you only have ONE rez, and its on a long *** cooldown.
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FOR PONY!