the way I see it, Holy gets just over double the duration on the cheap healing effect (23 second compared to Disc's 10) so while Disc will get the benefit more, Holy will get it for longer per activation, or at least that's the way I read it.
as for the 4pc....yowza... no way in HELL that's making it live 10% chance for a superbubble... very very nice... and when that superbubble pops... 14% mana return.. EPIC, I can see it being tooled back to say 50% bonus mana