Anyone had any success with Rengar yet?

I feel like he's simply either used as a token Assassin or token Wild (usually not wild, since Nidalee, Warwick, Ahri and Gnar are not only better but offer better synergies).

I tried stacking a level 3 Rengar with IE, Rapidfire and Shojin in a 6 Assassin 3 Void comp and sure he was oneshotting people with his basic attacks as any assassin would but his ability took so long to activate and when it did activate it dealt far less damage than his basic attacks.

On top of his subpar ability, it bugged out a lot too. If his target died when he hit full mana, he'd simply not use it and expend all his mana anyway.

The only good thing about his ability was the crit chance and attack speed that allowed him to oneshot more people faster. IE was probably unnecessary, but I wanted to see how much his ability would do with it + Assassins. Turns out it can't crit though feelsbad (or I just got reaaaally unlucky literally every round).