When I first saw kayles unique "instant" projectile attack, I thought it would be a pretty amazing mechanic.
But the more I examine it, the more I realize that this is probably actually hurting kayles ability to get kills.
This is because of how ranged attacks with projectiles "Chase" people when they're technically out of range of the attack. Generally players will run away based on an HP cue. If a projectile is still in the air when they run away, then its much more likely that a kill will be scored. With kayle, because none of her projectiles are ever "in the air" state, I find that enemies tend to get away much more often with flash/blinks etc.
TLDR: Would kayle benefit from having an actual projectile with travel time over her current "instant" splash ability?