We're not low DPS in PvE... I agree compleatly, but that's because mobs usually stand still for the duration of master strike, which if you pay attention to the tree is 1 of the 4damage abilities that we have to priorities.
In PvP master strike is utterly worthless, even when slowed people have plenty of time to move out of range before the third strike lands.
I think it's fair that it can be interrupted, but the fact that we have to stand still to channel it seems silly to me, we're a melee class we have to be mobile in PvP, since ranged classes will want to kite us and we want to chase them.
So taking master strike out of the equation, we're left with plasma brand, OH slash, and blade storm... already we've lost a little of our dps and then we have a problem with plasma brand as well which has a dot that lasts 3 seconds longer than it's cooldown, thus making us shave valuable damage off we re-apply it when ready.
Say what you will, but If Bioware either let us move during master strike or gave us the ability to immobilize them for the duration, and lowered Plamsa Brand's DoT duration this tree would be able to do very well in PvP.