The cast time hasn't been reduced whatsoever - this represents the entire risk when using dizzying.
You therefore can't reduce the damage without adversely affecting the risk v. reward tradeoff of the skill. And it's already not in a good spot on live.
Expecting an average DPS increase to compensate for this is completely asinine for various reasons:
1) It's still not close to BiS for PvE stam DPS.
2) No one in PvP is going to land multiple dizzys in a row to allow a mathematical average to emerge. You land one, two max, as part of a burst combo.
3) People are reporting that the post-global removal isn't even working properly, and we're less than a week away from Elsweyr.
This situation is a big steaming mess, and the worst part is nobody even wanted ZOS to mess around with dizzy in the first place. And now they're too busy d!cking around with back-and-forth NB changes to devote any effort to fixing this.
Just revert and be done with it, gosh.