Regarding the usefulness of sapping as a strategy.....
There are 2 possible debuff effects that, if either were applied to Electric attacks across the board (excluding maybe Melee, which is already strong), would increase the viability of blue-bar attacks.
The first is a negative-value "conserve power" applied to mobs (but not necessarily pvp), significantly increasing the cost of every ability they use. This would mean even after they get that "tic" of Recovery, it won't last for many attacks, and they'll be drained again.
The second is kind of out of the box, and again wouldn't apply to PVP. What if we make a new debuff for PVE, that makes it so that every time a mob uses a power, it ALSO costs some HP? That would mean either 1: They slow down their attack rate (the main goal), or 2. They die faster (thus making Sapping still an effective killing strategy).
Whichever debuff is used, I suggest a good name for it is "Power Bleed," suggesting that rather than conserving power, the target is losing/wasting power with each action.