I don't that Rammus isn't that insane.

What's happening is that AD, whether its lethality or crit, is so fucking strong right now that team comps are getting away with only one magic damage dealer, but rammus provides a powerful check on that because of the insane amount of anti-AD capabilities he brings to the table.

Nerf lethality AND crit a little so that magic damage dealers have more room to breath and he won't be too bad.

And for the cherry on top, you can completely remove the flat 10 mr increase on his W, and also lower the MR gain during w by 5% at all ranks.