Yes, it's normal, as the barbarian camps disappear if: - they have been raided 5 times in a row, in which case they disappear immediately after the 5th raid (note that these 5 raids can be initiated by different players, what counts is the overall number), or - they have been raided at least once, and some time has elapsed since the last attack. Those barbarians that have disappeared or those that have been raided 1-4 times, will be replaced by new barbarian camps, which occurs every 6 hours.
