First, there's nothing systematically "wrong" about this ability, so this isn't a bug report.
What it does: Allows the Arcane Archer to fire a single arrow at a target (creature, player, door, headstone, herb, anything highlightable). It will then explode for fireball damage with a DC that scales with AA level. Use: 3/day.
What I propose changes: Allow the ability to also target open space, much like the actual fireball spell. It's relatively difficult to make use of this ability aside from the initial "pull" of a group of mobs, due to friendly fire. I've more often been making use of doors or random herbs as an anchor for the fireball spell.
That's pretty much it. Weigh in whether you agree or disagree