After some thought, I decided that I like the "official" version the way it is, for now.

However, if your GM would be more comfortable with lower power, might I suggest the following changes?

1) The "Instant Murder Flash" half of the maneuver grants 10d6 total bonus damage, that you may split up among targets as you see fit. (This may actually be a little low, consider raising the total to 15d6 or 20d6.)

2) You may only continue to make attacks as long as you hit. If you miss a target, you must either stop attacking (if less than three targets are dazed), or move on to Blood Press Guillotine (if three or more targets are dazed).

This way, the maneuver is still somewhat useful against a single target (10d6 + daze), but you won't be murder-flashing an entire army.