"Rumble's doing somewhat decent in the jungle, so we're going to ignore his 42% top lane win rate"
Is pretty much what I got from riot's last set of patch notes. He's literally game-breakingly horrible in top lane, and isn't actually that brilliant in the jungle (48% win rate, not accounting for the fact that a disproportonately high percentage of players are experienced with him). He's not tanky, he doesn't have excessive mobility, his CC is meh at best, and he can't stay relevant in damage while building tank like others. It's frustrating that his massive failure in his primary role is being ignored because his Q doesn't do reduced damage to monsters, giving him an overloaded clear time.
or
, pick one), which are cheaper than his core mr pen items on top of that, 1600g for Haunting Guise vs 1300g for Hexdrinker or 1100g (!) for Spectre's Cowl, given the fact how horrible it is to last hit as Rumble is quite ridiculous if you ask me.