As a healer it took me a while to get used to the reduced mana cap, but now that I've adjusted and figured out how to weave my mana-free (or in the case of WHM mana-negative) spells with the costly ones and Lucid Dreaming, it feels a lot better.

RDM I probably play entirely incorrectly (not my main class, so I don't really care), but I've been working on sustainability for that side of things as well. That's mostly coming down to figuring out the best timing for Manafication so I can get a second melee combo in. I've found that if I hit Lucid Dreaming right before I start the melee combo, that gives me a good bump in my MP, so by the time I Disengage back to my casting combos, I've got about 15% MP back. If I can combo up enough black/white and Manafication for a second full empowered melee combo, that's even better. I still end up pretty low on mana by the end of a long boss fight, but I rarely drop into "not enough to cast anything" range.

But like I said, I probably play RDM all wrong.