Im running:
Paladin (Tank)
Druid (DPS)
Mage (DPS)
Shaman (DPS/Healer)

And my mage is dying, alot!
With this team i havent had any major problems with normal dungeons in WOTLK. Whiped a bit in Nexus when i tried it at 70, but after 5 runs im doing it easy mode at level 70