Upon relogging the overseer missions "The first Recovery", "The first Recruitment: Kelethin, "The first Recruitment: Ak'Anon, "Uncommon Conversion" complete. Can be done all day long, leaving you with unlimited heroes.
Tested it on 2 of my accounts and it doesn't come back for me. Well Uncommon Conversion does but that is part of the reward this quest is just an instant one that kills off weaker agents to make 2 better.
Yap problem is rather that all "The First Recruitment" quests keep refreshing all the time ... They are 5 sec quests and give 9 Overseer agents each