Someone posted in a thread saying that bard at 50 plays pretty much like bard at 60, instantly invalidating everything they have ever said now or in the future due to not knowing what the hell they are talking about. Minuet, Empyreal Arrow, Sidewinder and Iron Jaws become class staples at 60 that you don't even have prior to 50. Bards have basically double the mandatory use skills at 60 than they did at 50. Machinist is the same what with gauss barrel completely changing up how things are played to cap.

Ditto Dreadwyrm trance et al for SMN, ley lines and enochian for BLM (Not that I've ever played one).