I tumble all my ammo primer-in, because I don't have the time to make decapping a separate step. If I were going to start tumbling rifle brass, the higher pressures would concern me enough I would buy a decapping tool and take the time. If you load a cracked case into most pistols, nothing bad will happen as long as the crack doesn't get exposed before the pressure is out of the barrel.

I've learned that having a cracked case will make a unique sound when "jingled" with other brass. If I hear that sound as I'm transferring cases from the sieve into the case feeder I stop and inspect.