There are lots of ways to approach this, but if you're gonna go without RAF or boosting, you really want to consider what you will consider the most fun to play, as you will be looking at them for a LONG time! In MY OPINION:
- I'd reconsider using a warrior as your tank. Not that they aren't good tanks, but they require a lot of attention, that makes boxing them tougher. Plus, while leveling, they don't add much to the team, until you get into instances.
- How about a five caster team that can be converted to tank + healer + 3xDPS when you start running instances. At least until you get to outland, there is little need for a real tank or healer, and the five DPS can blow stuff up very rapidly!
-- Something like a Feral Druid (future bear tank, caster while leveling) + Holy Priest (future healer w/ great buffs) + Boomkin Druid (DPS, Buff) + Frost Mage (DPS, buff, food, water, portals) + Destruction Warlock (DPS, phased Imp for health buff, healthstones, soul stone on healer) A team such as this would prove interesting to develop and play, and blow through world PVE with ease.

Anyway, good luck, and keep it fun! :P