Your expectations may be too high. Mallet is a gunslinger like Jim Kelly. You have to take the bad with the good. Kelly averaged 21.5 TDs per season in his Bills' career but also averaged 16 INTs.
As we've seen, most of the college QBs with amazing college stats (Colt Brennan, Timmy Chang, Chase Clement, Kingsbury, Graham Harrell, etc.) are products of their systems and don't make it in the NFL. QBs from the major conferences, with less impressive college numbers, are usually the ones that make it, especially because of the competition they face.