Well, since Slobber's passive is a ranged attack, and it's arcane ability is vomiting out a pool or some sort, it doesn't matches. For example,

An enemy is standing right in front of you, and Slobber is currently shooting out his ranged attack. But at the same time, you activate his ability, it vomits right in front of him, not on the enemy.

So what I am trying to point out is that, make his vomiting straight onto the enemy, not in front of him, doesn't damage the enemy unless you lead them to it.