They probably have to strike a balance of some sort. Back in the beta, thats all most mages complained about, MP regen. Of course, that was back when you had to do a ton of actions in a party to get decent SP...

I dont think auto regen of MP (like rest in XI) is a bad thing in itself, since MP recovery skills should be used to quickly regain magic during a really hard battle/series of battles where time is of the essence.