This definitely has ups and downs. In my opinion, it really seems like the devs are eager to make their past dungeons obsolete. Dumping the old world raids with the launch of the Burning Crusade made a lot of sense, but rendering most of the pre-Sunwell content obsolete with badge gear within the same chapter of the game seems a little strange to me. Even if the vendor was in the raid zone itself, giving a wider selection of gear to those who have cleared Black Temple and Mount Hyjal, that would only lead to those with a plethora of badges paying for a raid ID for vendor access.
Of course, this could be a very good thing for people sitting on many, many badges from Karazhan and are trying to gear up for Wrath of the Lich King levelling. Black Temple loot in exchange for a few Kara runs? Sure, I'll take that!