on-hit works on WW plenty good in Dom. yal forgetting that the on-hit build is rather cheap, so mid game you dominating allowing you either win the game sooner..

I actually had a lot of fun playing On-hit Teemo before I started going AP/atkspd Teemo. it's a slightly different style of play.

AP Teemo is much more supporty and magey. Teemo is always engange>disengage hit and run. But AP Teemo is even more so. Mushrooms are an essential part of his playstyle and you must master the Teemo Zen Mushroom arts to get full use out of it.

On-Hit Teemo is much more of a duelist. Especially once he gets Malady, Wit's End, Phage/FroMal. He will have a fairly reliable slow on the enemy and more survivability, which allows him to stay in one place and lay in the dps a bit more. Champions without reliable escapes are doomed. Mushrooms are mostly just stuck in high traffic areas for visibility or in future escape paths.

I mostly use mushrooms on escape paths, to ward health or towers, and for extra damage against melees to either kite them, or just for the damage, if they're too sticky and I want to duel. Also if I get ganked and know I'm going to die, or get stuck in the middle of a group of enemies for any reason, it makes for some nice farewell AOE before I fall down, a nice parting gift. :P

Hell, I've gotten double kills, even a triple, after I'm dead with a farewell mushroom, that's great :P