I got Final Fantasy XIV Gil that. I think you misunderstood what I was saying. ...Or am I misunderstanding you? It is late, after all...

What I was trying to express was that it isn't exactly the same situation with BLM and BRD/MCH using WM/GB. Sure, they both have to stand there and cast, but - correct me if I'm wrong, as this is hearsay on my part - FFXIV BLM cast times tend to be longer than BRD/MCH cast times. The damage bonus from WM/GB overcomes most if not all of the damage difference between FFXIV BLM and BRD/MCH. Considering similar damage with lower cast times, removing the sweet spot entirely while using WM/GB would likely cause BRD/MCH to become a little too advantageous in PvP.

Assuming what I said above about cast times and damage is true, it would probably be safer (for the sake of class balance) to greatly reduce the damage reductions placed on the BRD/MCH while not in the sweet spot so long as WM/GB is up.

The damage difference is applied after all said and done. Even with a 30% damage boost (and you're losing auto attacks on top of this, mind you), a 50% damage penalty (yes it's that high) will have everything hitting like wet noodles and the best you'll do is interrupt casts (which...auto attacks can do, and you can time your hits against their cast times without having a cast time yourself).

A BRD/MCH will not come to the same degree of damage as a FFXIV BLM. Even with WM/GB included (as well as all the abilities attached), they're still doing comparatively less damage relative to the other classes who are using their 3.0 tool kits as they were in 2.0. What was a 10% difference in class damage output in 2.0, is still present in 3.0 if all classes were using their new FFXIV Gil skills.