Of course what you've read on the spoil (including Giger's "SPECTRE") is subject to change, so will be the whole idea when posted; the idea behind this "BERZERKER" ability for the grey (veteran) warrior is to give him some sort of "Turbo" mode xD to be used from time to time previous exchange of the life of one of your still blue mates. (remember that the "victim" can escape the "murderer"
, you can bug out and call It even, or you can also be succeded at the QTE in case you were already grabbed).
I might sound a bit cruel towards the "victim", but remember that all those warrior players who molt into the grey and many times powerful veteran warrior, have done so because they have killed a lot of marines and earned a lot of XP, so they somehow earn the "right" to use this "incentive" no matter they have to kill one mate in order to take advantage of this. An assasinated warrior automatically re-spawns, he hasn't have to wait many seconds for It, and this isn't exactly a bad trade (for the alien team) since BERZERKER warriors will wipe out marines with extreme ease, believe me. BERZERKERS become stronger than the giger-alien (not than the superior runner or the praetorian), and have double ammount of HP at their disposal, so I think It may be a good trade for just the life of one mate who will re-spawn in zero seconds after beign killed.
I understand what you say about the same player beign 5 times killed in a row (for example) by the rest of their mates who already molted but he still didn't hahahah (or an even more irritating situation for him LOL), I know that could be difficult to stand, but..., nothing can be done in this regard imho.