Not from my experience, last Mordor I used roughly 500+ tops and ~200 highs and didn't get skills I wanted. That plus high grade life stones were very rare and, because of that, insanely expensive (up to 200kk each), while normals/mids were literally useless.
So no, personally I don't think it needs to be nerfed. If anything, changes to the LS drop rate should be made since tops were way to easy to get when compared to highs.