If you ride in rocks sooner or later your pipe will get dented! Even not in rocks (my KTM pipe got its first dent on my second ride - a log jumped out and got it!).
Consider a pipe guard - the flexi aluminum ones, or perhaps a carbon fiber one. I was told however that in some cases a pipe gaurd while it will prevent the dents, ends up resulting in "tweaking" pipe alingment when it is hit (the energy gets trasnfered to the mounting points rather than being absorbed by the dent being made). Keep in mind, i was told this by Pacific Crest Pipe repair. According to them, it is much harder to fix an alignment tweek than a "simple" dent. They may be biased, but I think he was not just yankin my chain about that.