I don't see anyone saying that blackmage is the "infinite mana shift class" either, even though that is kind of the only thing they have going for them aside their numbers.
I've also heard people throw the argument around that counting on many rezzes during progression is actually counterproductive, because you don't get to train your rotation for the case you actually WANT - people surviving (hence why I stated "perceived" support in the OP).
Why would you never see another verraise if it was behind 50 white mana, exactly? You can get that without even causing a mana imbalance, if you wanted. And my other proposed changes would even let you churn out a verraise every 10 seconds max on top of manafiction at the cost of much of your dps. But if you have that much to raise, I doubt having the usual dps would change the outcome of the encounter anyway.