Well, I think it's important to distinguish shield "dropping" and shield "diminishing". Diminishing is stuff that does a set number of damage to the shields. Tachyon beams, CPB, target shields, and plain old weapons fire all do this. When I hear shield DROPPING, I think things like the target shields proc, the phaser proc, shield power being brought to 0, boarding party, etc. The difference is, "dropping" a shield doesn't affect its current shield HP, it just stops it from protecting your ship for a time. Once the debuff causing shield facing(s) to drop goes away, your shields will return to right where they were before it happened instantly. You don't have to heal them to that point.
As for the "blacked out abilities" thing,, this sounds more like tricobalt mines or photonic shockwaves to me. VM doesn't go to work powerfully enough all at once to just reliably disable all of someone's powers like that.