No, I'm sorry, but there is just no way this change was warranted. Nidalee saw use because she's strong in the current meta. Taking her durability away is not going to change WHY she's been seeing use - all it does is punish you for no real reason.
Let's compare Nidalee's cougar to some other AP melees.
Katarina is known for her high mobility and burst. She's got a safe escape/engaging skill with a range much higher than Pounce, her ratios are much better and she has 4 damaging abilities while AP Nidalee for all intents and purposes only has two. These skills have excellent synergy with eachother and while she is fragile, she has enough damage to let her get in, do her job and get out.
Elise is very like Nidalee in that you skirt the edges of combat flinging poke until you can commit in spider form. Not only does Elise get her ultimate at level one while Nidalee does not, she too has a better gapcloser/escape, a better execute, hard CC in human form, and shreds bruisers with only spell penetration. She's also allowed to keep her defensive stats. And did I mention she gets access to spider form at level one? Yeah, that's kind of an important point.
Akali is another high-mobility AP champion that is melee and relies on skirting combat before jumping in and blowing all she has. Her shroud gives her defensive stats as well as invisibility, her charge can be used more often and has roughly TRIPLE the range of pounce, and we all know about Akali's burst damage.
Now, Nidalee isn't just about her cougar as we know - but her human form is already pretty crappy. She has two spells useful for teamfighting, and one of them is her heal, which has already been nerfed and drains a ****ton of mana. So now all she can do is stay in that unfun human form tossing spears hoping she can hit someone who isn't a tank by hiding around a corner, which in itself puts her in a vulnerable position as her team will probably be squaring up to the other a bit away from her.
Even Quinn, while using her ult, has it better. She has a blind, to prevent some incoming damage. She has a massive attackspeed steroid, which as an AD champion, is fantastic. She still has heavy sustained damage and burst with Skystrike and her other spells. Yeah you don't give her any defensive abilities, but that is the main theme here - she doesn't NEED them because she does enough damage to kill her target and get out before they kill her.
There is no "BUT IF YOU'RE SMART YOU'LL BE FINE!". I don't know what fantasy birthed this travesty of a change, but it is NEVER going to happen that you get in cougar form without being noticed and you get to go anywhere near anyone - no matter how low - without being stunned and bursted down. And it is NEVER going to happen that you get the drop on someone and manage to do more damage to them than they will to you before their friends come running.
Nidalee is not in a great spot right now after these changes, because despite you buffing swipe's ratio she STILL does not do enough damage in cougar form to be worth the risk of using it in a teamfight for anything except cleaning up, and her only damaging ability is her easily-dodged Javelin Toss in human form.
If you try to go cougar in a teamfight, you will be blown up instantly, making you choose to either become tanky enough to last more than two seconds - which will mean you simply do not have the damage to earn your space on the team - or going glasscannon - and exploding the second anyone comes near you, keeping you standing miles away from the fight chucking spears because you have no cc to protect yourself or your teammates and your heal already got gutted ages ago.
Come off it, pounce is NOT going to keep you safe when every bruiser has CC and a dash and can't be killed. Nidalee's durability before allowed her at least time to escape, and meant she wasn't killed by errant AoE when trying to chase people in won team fights.
tl;dr: Nidalee DOES NOT DO ENOUGH DAMAGE in cougar form to make using it as a reliable source of damage worth it, because now she dies in two hits rather than three and her ratios are still horrible. And why do Jayce and Elise get to keep their defences when they have a much stronger kit and both get their other stance at level ONE?