So since blizzard has once again implemented a quest/system that at launch is already failing. The above mentioned boss will not give credit towards the world quest for it, however it will give you all thee rewards and count towards the jailer efforts.
There is an exploit though and I highly advise no one use it as I can guarantee blizzard more than likely will ban players potentially. If you try to kill the boss numerous times, it will continue to count towards the jailers efforts bars., I suggest not killing him more than once in case they do something silly and ban players for simply killing the boss more than one time.
Leaving the group before he dies also didn’t work, so we’re SoL until they fix it, great game honestly.
Good PSA but I sincerely doubt they will ban anyone for completing a weekly slightly faster. Now if for some reason they could redo the weekly over and over then yes that would be grounds for a ban but not this.