I think people are misconstruing my problem (which I might not have been clear enough about). I'm less concerned with the potential to kill lots of opponents in the same zone or even about damage (mostly), since I am not changing the Weapon ratings. Folks who can pull Power 5+ are still hitting hard. My problem is with the ability to hit unfailingly. Simply, defenses do not scale to how "to hit" rolls scale for wizards, if you include control bonuses. Even magical defenses, like the +5 block your average wizard will throw up during a fight are practically useless against someone with some refinement and good foci who has a base +9 to hit you. Similarly, that individual is going to have any easy time hitting anything with less than Superb Athletics and Mythic Speed. I don't feel like this situation reflects the books at all, where magical shields are shown to be very effective and fast monsters are shown to be tough to target. Most wizards are going to have +4 or +5 Discipline to begin with, so they are already expert marksmen. Giving them at least a +2 bonus to hit on top of this makes them nigh-unstoppable, particularly since they are hitting with Weapon 4+ attacks.
I don't feel that addressing that "nerfs" wizards. They are still throwing around attacks with a Weapon rating that outstrips anything less than a tank or a demon with Claws and Mythic Strength and their magic gives them unparalleled flexibility. A monster's claws are good for one thing, a Wizard can do /ANYTHING/ given time and prep. I just don't think they need a "to hit" bonus and the attendant extra damage this gives them, ON TOP of these advantages.
And, as I said, my concern is less about my PCs power and more about their enemies. The PCs are losing a couple points of stress in damage and are missing a little bit more. One tough NPC in my current major plotline is going from a +8 to hit to a +4, meaning that the PCs shields and dodge rolls may actually save them from his Weapon:8 attacks (I calculated that, if they didn't get a shield up in time and rolled badly on their dodge, they could potentially take 20 shifts of damage from one of his attacks).