1-Disable PvP in atoll, it's not fun & not profit for anyone no matter you win or lose. Reason: please see this post

2-Atoll Boss should spawn after a player or party has killed a certain number of mobs (let's say, 30, which is the total daily rewards attempt), or, in a much simpler way, just turn all mobs into a boss when the 100 count has been reached & turn them back to mobs when at least one boss has been killed. There's no point to encourage players to compete for the boss & stir up more drama when the server is already dead enough & full of unhappy & frustrated players.