Near the end of TBC when we first heard that Naxx was going to be removed from EPL and moved to Wrath content as the first raid, I went with a 25-man raid group who had done everything but the new raid (Sunwell) and were pretty much geared to the teeth. One of the more memorable wipes is that room full of mobs getting to Heigen.
Fast-forward to us being level 80 and entering Naxx. We blew threw that, we blew threw pretty much every wing. It was a very weird feeling because it didn’t seem like it had been tuned up.
We knew the mechanics in both cases. We were the same skilled people. Our gear was actually on the pre-raid BiS end in Wrath compared to the post-raid BiS in TBC, and we were ten levels OVER rather than at level.
So I think scaling was the big flop there.