I don't mess with sliders or effect anything that would have anything to do with the passing game on madden. As far as player ratings in regards to QBs.... the only thing I've done is lower RGIII and Kaepernick. I've raised the ratings of Brady, Rodgers, Brees and Ryan. I also raised a couple back up QBs (Matt Moore, Chase Daniel etc.) I've done nothing that would make passing any more difficult though.
Matter of fact, Ive become much more pass dependent in my franchise and have had great success with TE's and #1 WRs.