This is my first time jumping into season play via adventure mode. I watched Bluddshed and Raxxanterax do the Zoltan Kulle bounty on their YouTube channels and each had a large chest full of goodies to open after defeating Zoltan. I did the same bounty twice and no chest. What’s going on?
You can kill Kulle anytime by accessing his waypoint, but in order to get the chest, there has to be an official quest out to kill Zoltun Kulle. This quest isn't up all the time. You might need to open several games and control the Act2 bounties, to see if the Kulle bounty is active.
Remember there are 4 possible boss bounties in Act II: Belial, Maghda, Kulle & Vidian.