That isn't true at all.While you can argue that during that time, RAW was in a slump, and true, it wouldn't really take much to improve it, but Punk took that 2.7 rating and turned into a 3.4 or 3.5 if my memory serves me right, and that's a huge rise just for one person. You could argue that it was just for the mere shock, but those ratings continued over the weeks.. while not as 3.5, around 3.3 which is still strong.
The ratings never dipped below 3.0, and the only reason the ratings went up was because of the Draft. In it's normal timeslot, the Draft scored a 3.7 rating. Punk's win the next week did a 3.5, as did the following week, and then the ratings went down to 3.3 and below.
So, not only was it not Punk who made the ratings go up, you can clearly make a case that he was the reason they went down.