Is Mundo Too Nerfed?

I just had a very nicely played game. I went as Rammus in the Jungle. ok. So cut to the point- late game, I manage to hold this enemy Mundo under his turret while my ADC Ashe detroyed the turret. We ran him off to his Inhibitor Turret- I grab aggro, and Ashe melts Mundo, I skate out without a problem. HOW?? I mean, not complaining- but Mundo shouldn't have had that problem. I didn't even think it was possible- but I play my roles seriously, and I'm glad I gave Ashe the benefit of doubt.. but- come on... It's Mundo- there needs to be some challenge.