Killing the lead does hurt more than killing one of the followers, however it in no way stops the others from working. If the main dies, the othes will still perform all commands they normally would. Plus you can Alt Tab and take control. not as effective, but if his bots are just standing there, hes not doing it right 
additionally, multiboxing for PVP is Hot garbage and should not be allowed. Blizz seems to agree with this opinion by removing the follow function in BG’s.