The issue causing lag seems to be the physics check for the attacks.

Why not just remove that from the off-hand attacks, if the main hand hits via physics check, then the matching off hand attack counts as a hit per the physics engine.

One less physics check for every off-hand attack?

That should be enough of a change to lower the lag.

Backing out every other swing seems to be the only "exploitable" portion of this, and it gives no benefit that I see, and would be pretty much impossible to do.