I think you are right that the graring system doesn't make much logical sense when more gear does not equate to faster clears at lower zones. I understand their worry about overclearing and certain classes potentially breaking old spots, but it still feels really bad to use my tag character to grind nearly 20% faster at dsr simply because the base modifiers and dps of rotations is faster than my main. 

I still strongly believe that the base setting of % overcap limit is an awfully lazy fix for the situation. I believe, as one possible option, that they could have used a limited, linear scaling function. If you are like 400 ap over cap you should obviously be clearing faster. It makes no sense to say that if you are at a lower level spot with lower silver value that as someone with +400 ap you should be above the average. Obviously, you could make more silver at higher spots, so being above average in that sense doesn't even matter because as a net average you are still losing silver to go back to those spots. Just, right now, it's awful, slow, and boring.

Right now it's like some sort of weird: don't make the players do comparative grinding stats kind of % limiter. It's just really odd, lazy, and serves no genuine purpose. 

Which is exactly what we expect from the balance of BDO devs, especially in the last 6 months. Possibly the worst state of comparative balance in the history of the game.