Every expansion or major patch, we get slightly better gear (or in the case of Burning Crusade, incredibly superior gear)...

Pretty good business model, anyone who took the time to gear up, will likely do so again, and yet it is almost a reset, in that a fresh 80 was on fairly even footing with the top 70 raider on the server of their class, upon freshly dinging 80th.

Sure a content patch isn't exactly the same thing, but still ToC > Ulduar > Naxx level loot.