I don't know if anyone else has said this, if so please feel free to dismiss it / correct me

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Maybe AV can only use 2hrs that are currently available to members of the alliance that has it claimed? IE. If a whm can use benediction, AV can. That's why they all fire them off, to keep him from using them. It would essentially make AV a 2-hr free fight, for both him and the players. The one condition of this may be that AV has to use a 2hr first, then the players go to "lock" their 2 hr. (underlined because I know someone is going to read this and say "We've tried using 2 hours before to stop AV from using them, etc etc)
It would also explain them using using their 2 hours again in theory, if the timer is back up for a player, AV can use the ability again. Idk, just a thought.