To be fair, according to champselect, Nidalee soft-counters Renekton and Garen. AD Nid naturally has a strong laning phase top lane, since she's a ranged champion vs. mostly melee champions, that much is natural. Later in the game she transitions into a split pusher; she doesn't have too much team-fight presence without the nuclear tipped spears, and that she has no CC to speak of, very little AoE (two cougar abilities, which, since she's building AD, don't deal too much damage), and very circumstantial assassination/burst potential (unless she's super ahead, it usually will take at least two cougar rotations to kill a squishy, which I think is comparable to something like a Renekton).
Also, Nidalee is a form-change champion; they're naturally incredibly strong at lvl 3 since they have access to 6 spells at that point (to compensate they don't get as much of a power spike at lvl 6 because they lack a true ultimate). Additionally, Nidalee is incredibly squishy through lane phase up until after she builds TriForce and starts building more like a tank. Even then, she's never really a true tank; there's nothing in her kit to compliment a tanky playstyle, she just has to build this way so she doesn't get blown up instantly when she goes into cougar form. Additionally, she's also very mana hungry, so while she can sustain health in lane pretty well, it does put a huge drain on her resources, especially if she isn't building AP to improve her heal, or building mana/CDR so that she can heal more often (the only mana she typically builds is from Trinity Force, which is maybe one and a half heals at lvl 9, if she's maxing E). It's a huge drain on her resources too, since she's not only using the heal to sustain herself, but also for the AS boost to trade better.
Again, ranged champions naturally have an advantage over most melee champions in the top lane; this is another reason why Teemo is so obnoxious to deal with in top lane, why he's often picked to counter relatively immobile champions like Garen or Nasus. The counter, therefore, is to pick a champion that either has a reliable gap closer and better melee capability, such as a Fiora or Jax, or who has range to counter Nidalee's mostly auto-attack harass, like Gragas or Lulu.
For the record, I mained AP Midalee for a long time, and yes, I do think she could use some balance changes for her in top lane, specifically the reset on her pounce is a bit excessive; I think that Riot largely added this change for AP Midalee, since she is super squishy without tank items. I don't know if Riot will be looking to balance her as a top laner after changes have sort of forced her out of mid lane; if they do decide to keep her top lane, they'll probably change up her pounce as it gives a ton of safety as it is; basically Kassadin ult you can have at lvl 1 and costs no mana (albeit deals less damage).
going you'll be the dominant force. I'm guessing Gragas would largely be the same way. The burst she has is kinda nuts though.
