Stuns on covy leaders.

Now everyone nows that the prophet can be stunned by a single vampire when hes flying, so why cant the brute chieftain and arbiter be stunned? Im not saying by one flash grenade or brute shot but atleast 4-5 should hit. Otherwise it is unfair. The cheiftains stun has to hit the arbiter 10 times to make it fair on the arbitier otherwise its alittle unfair, but what do people think about the stunning to covy leaders idea?