Don't underestimate the power of 10 HP. The amount of EX Pokemon with 170HP and the amount of non-EX whos atk does 80 dmg is big. (To demonstrate the true power, take DeoxysEX(PF) vs Espeon(PF), with one energy you could two-shot the Deoxys while it is still on the bench) Not to mention it serves the same function as Virbank, alowing you to oneshot 180HP-EXs with a laser at hand.
I think it would be a great balancer to the format.