Sorry I didn't mean to sound critical. Have you maybe tried lowering QB/User accuracy below the 10 limit? I've tried a few sets which have very low QB accuracy and although you have a few more errant throws by your QB it does still seem tied to their ACC. So with Luck it's not horrendous, still get around a 60% completion rate. It does seem to finally get the CPU making bad throws too.
I'm sure the INT Grounding penalty slider makes a huge difference as well, but as with all sliders, who actually knows how it works?! :P