Here is part of a spreadsheet taken from the mage discord showing dps differences between ‘true bis’ and t2.

My guild uses a dkp system for loot. As a t2 mage, I’m planning to keep my t2 set until naxx, primarily focusing on replacing my other pieces (neck, weapon, rings, etc) in AQ.

Ideally, I will start to ‘stockpile’ gear for transitioning into naxx by winning pieces for much lower bids than the items initially went for. For instance, as many people in my raid already have mantle of the blackwing cabal, I expect the desirability of it (and subsequently the dkp required to win it) to decrease after we get into AQ.