I can't say if this toggle thing is over-powered or not, Warriors now (the kitted ones) are flat out brutal... I've seen multiple people die in the past couple of days before they've even been hit on my screen (or theirs) sometimes by a 1-shot or sometimes 2 shot by TDB Swings.
I suppose the problem is that the scenario regularly occurred where squigy players are saved by a TDB/Slaying combo, actually giving a person the time needed to react & escape and count there lucky stars & now that scenario is dead with the Slaying Toggle it's going to annoy a lot of Wizards/Assassins/Archers/Maybe Taoists who get 2 hit - especially at later levels when Warriors are very solid and can tank multiple attackers with ease compared to every other class.
I think at the very least they should have sorted out this Cast/Walk issue before buffing melee, as that's currently horrible for a casters gameplay when fighting melee... Cast a spell & miss then you're forced to walk a few steps before you can run away, ultimately you just to get smashed in the face by a TDB & have to RT.
The global cooldown on skills also makes life hard on casters - Basically the melee gameplay is extremely fast and fluid while the Casters gameplay is extremely slow due to this cast>walk & 1.5 second global cooldown.