Instead of Nerfing Champions So They Don't Destroy Top Lane...
How about, top lane has some kind of passive effect over it, let's call it "Mana Void", that reduces mana regen by X% while in lane.
Champions designed for top lane who are unduly affected by this can have their mana costs adjusted so that they can survive, and (mostly) ranged harassers who have pushed out the traditional top laners will be forced to either build full mana or stay away from top.
Thoughts?