Is this normal?

A while back, John was kind enough to give a pair of 29er Kenda Nevegals that he couldn't use. I put them on the RIP9 and have been very happy. They hook up well and I don't have to worry about them even in nasty terrain. But they seem to wear quickly, and after my last ride I noticed a couple side knobs torn off. I guess that means I'm cornering hard? P.S. I have the Dual Tread Compound (DTC) version.

Notice that the side knobs have ripped away while the siping is still intact.