Rain of Arrows is an Archer ability that functions like Fireball, in that it hits a 3x3 square. Also like Fireball, the center square does not have to be occupied. However, the game's code frequently has trouble figuring out what to do when the center square is not occupied. When I say 'trouble', I mean, 'doing nothing for up to 10 seconds, then working right'.
-Issue seems to crop up most when target square is far away from attacking champion, but not always (sometimes occurs when target is quite close, as well).
-Issue seems more likely to occur on first turn of combat.
-Issue is sporadic - sometimes it works just fine, other times it sits there twiddling its thumbs for no good reason.
-I have not tried this with different weapons yet. For the moment, all broken uses are performed with a Lightning Longbow equipped.
Edit: Updated with new build # because bug still exists. This has now also been reproduced with equipment other than the Lightning Longbow (which I miss dearly).
Edit: Updated build number again.