Alistar was nerfed because he was strong and Riot didn't want him to jungle

I don't remember Nidalee ever ganking me through my turret at level 2.

Alistar was nerfed because he literally came from YOUR turret, knocked you away, and there was nothing you could do to stop him. He literally ignored your turret to gank, and only farmed jungle for red + blue buffs.

It's actually fairly risky to jungle Alistar. Anyone who supports with him knows he has some mana management issues, and if you don't pull off your ganks, you are virtually useless. You'll fall off real quick. Trust me, I tried it before and you have to practice a lot to get his clearing good and get ganks to go perfectly.

I don't really know what nerfs you're referring to... which patch was it? I don't actually remember seeing anything in this patch for Alistar, but I could be wrong. I know a while ago people in the lcs were using him top because if you were quick enough I think you could headbutt, auto attack, and pulverize at the same time... I think, but I could be wrong.

Alistar had huge CC, incredible base damages, and his R gives him tankiness that can't be ignored. Lots of it to. With the new jungle item, he probably could jungle again.