I don't know why you would call Mijin Gakure useless. Especially in lowman situations, inside or outside abyssea - if you go down, you can get up (assuming you were smart enough to use rr before starting the fight/event if outside of abyssea), use rr if necessary (I always carry a rr scroll when on nin outside of abyssea), 2hr, and bam! you're back in action and quite possibly save the day. Or in this case, the fight.
There are other jobs who have 2hrs which really deserves an overhaul, much more so than nin and Mijin Gakure.
Oh and I dinged 75 nin 5 years ago, is that veteran enough for you?