Many specs have competitive builds, but this being Vanilla, require very specific items to achieve these builds. And by competitive I mean they will do respectable DPS, they still won't match the Big 3 (Warrior, Rogue, Mage) but they will be in the general wheel house. There are decent builds out there for ShadowPriest, Ele/Enh Shaman, FateDagger Rogue (prior to P6), etc... Will you be top dps, not really, but can you sneak up there if you have the right items, sure. If you are mid pack in the Mages you are doing fine. People get excited over min max but these are 40 man, ez raids, all DPS will have a spot. A raid of druids can down these bosses.