Nidalee's heal's AP ratios got nerfed pretty hard a while back (0.55), making her sustain up slightly worse. It makes AP nid top a much less viable pick, and against highly mobile champs like Riven or Lee Sin there's pretty much no point in playing AP nid anymore.
But even worse were the survivability nerfs on her aspect of the cougar, making her aspect of the cougar unviable against high burst champs like say Renekton, who are melee.
It's also completely useless for teamfights now. I mean, it was ALWAYS completely useless, but now it's pretty much a death sentence, esp now that she has 0 magic resist scaling, which I think was completely unjustified. This also makes her soft countered by ap tops now.
This doesn't really affect her split pushing, but it does make it slightly harder for her to survive a well coordinated gank. In general, it's just a big nerf to AP nidalee top, where it's harder to escape from ganks in the laning phase, since the lane is longer.
On the other hand, AP support nid has been continually buffed.
Spear has been buffed and buffed incrementally, mostly as compensation for those nasty survivability nerfs. Both it's CD and missile speed have been buffed, and the her base values have also been buffed (heal and cooldown). In other words, gold is less and less important on Nid, and if you manage your mana properly Nidalee can be a real terror bot lane with bush control, sustain, and poor positioning punishment.
Overall, I think that Riot is pushing Nidalee out of top in the misguided attempt to make "Nidalee Top easier to kill". The thing is, her kit makes her just really hard to kill top, and no amount of number tweaking will fix that. All these number tweaks will do is make her unviable top. One good thing is that nidalee is a better support now. League could always use more supports.