yes, int is great for mana regen
its quite simple: most regen is mana pool depends.
but...how many wipes were due to oom?
if the wipe is healers' fault, i think most of them are switch target too slow/oor/not be top offed... but not oom
so imo, only go int if your gears are two generation before the instance. eg run icc with ulduar.
otherwise, reckless and are the only gems we need