I knew plenty of people that started mid-BC and were more than happy to run Karazhan to gear up. It was just as fun then as it was the first day it was available.
Vanilla was very much the same. Onyxia and MC were active all the way up to TBC.As soon as that was no longer the case, this folded faster than a card house in a hurricane. Besides, the same was not the case in Vanilla. TBC is an aberation, not the norm.
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It's better, but it still plays into the really broken notion that everything needs to be about progression.