I've noticed that AoF's passive ability only grants you the extra turn when you kill the enemy you are currently targeting. This means that AoF's passive may not be as useful on a team with mostly AoE characters. If you happen to kill an enemy that you aren't targeting via an AoE move, then you won't be granted an extra turn. This bug makes it rather annoying to use AoF while autoing campaign levels, but also opens up some strategic moves in PvP.