Didn't Wenger come out in the past saying that the away goals rule forced the home side in the first leg to be more negative? If I'm not mistaken he suggested that the away goals rule only kick in during extra time, so the losing team still has 30 minutes to get things right. Not sure how it panned out with the UEFA higher ups, but I think its a pretty reasonable idea. Nowadays, teams playing at home in the first leg would generally prefer a 0-0 than score draw.