If you normalize the numbers on a per-attempt basis, then Schaub is still have a very impressive year. In my mind, there are 20 starting QBs worth tracking this season (Schaub, Rogers, Brees, Peyton, Eli, Roethlisberger, Favre, Orton, Brady, Rivers, Romo, Flacco, McNabb, Palmer, Ryan, Warner, Hasselbeck, Garrard, Cassel and Cutler). We can pretty much presume the stats for the QBs of the other 12 teams are putrid. Against those 20, this is where Schaub ranks on a per-attempt basis.
TD percentage (6.43%): #3 behind, in order, Brees and Peyton
Yards per attempt (8.33 yds): #7 behind Rodgers, Roethlisberger, Peyton, Brees, Romo and Rivers
Interception percentage (2.01%): #9 behind Orton, Rodgers, McNabb, Favre, Rivers, Garrard, Brady and Peyton. In other words, the eight listed get picked less often than Schaub.
Sacks pecentage (4.60%): #8 behind Peyton, Brady, Eli, Ryan, Flacco, Brees and Orton.
QB Rating: #4 behind Peyton, Rodgers and Brees.
The only QB ahead of Schaub in every one of those categories is Peyton. In fact, Schaub and Peyton are the only QBs in the top 10 in each of the above categories. Brees is #13 in interception percentage. Roethlisberger and Rodgers are at the bottom in sack percentage (along with Jay Cutler). Brady is #11 in yards per attempt.
So even if you control for the number of attempts, it is apparent that Schaub is playing at an extremely high level so far.