There was nothing wrong with it in TBC. Heroics were the top tier casual content (along with Kara/ZA if you wanted to raid), it was not supposed to be something you can mindlessly zerg through with 5 randoms. And Cata heroics had nothing on TBC. The class abilities have grown incredibly since then. In Cata every class had strong AoE (dps, heal, threat) and a bunch of survivability abilities. In TBC only paladins had AoE tanking etc.Quite frankly it was a bad design in TBC and inexcusable in Cata after the popularity and accessibility of heroics in Wrath.