Yorick has way more weaknesses that Rumble. First of all, he can be kited much more easily. Secondly, even when he was strong he still had big mana problems. He also needed damage items to be relevant (Manamune). Rumble can basically just build offtank AP items because his base damage is so high.
Also, I don't understand why you keep stating Rumble's passive like it's a weakness. He gets so many free stats, and even when he does overheat, your trade still isn't super beneficial with his enhanced autos. His ult may be hard to use perfectly, but landing a mediocre ult that does enough damage to be effective isn't hard.