So, instabought Elise and had some initial comments.
-Epic login music/story
-2 hp nukes gained through just 1 skillpoint (toggle R and Q)
-The fact that rappel has no damage, meaning if you're really low on health, you can hop over a jungle wall to a creep camp and juke without taking any aggro.
-1.5 second stun
-Massive attack speed steroid (deciding whether maxing frenzy or toxin is better. frenzy gives better sustained damage but as a jungler you usually want the hard nuke or cc.)
-Slightly faster than most other casters when in spider form. (spd=395 or so, compared to the typical 370-80).
-Spiderlings follow targets. It feels amazing when you set a spider like a mine and it starts chasing a champ. Great way to buy time to run. Also, I noticed that the spiderling, if it finds a minion and then a champion second, will switch targets and run for the champ. Great way to set traps and/or chase targets. It's also her most reliable nuke by far because of the awesome ap ratios. (I think it's around .8 or .9?)
-Cocoon has zero damage. As you level it, it's cd lowers but its stun does not get any longer. Assuming you max E last, you're stuck with generally zero boost to your damage output between level 13-18 (minus the ult/added spiderling), making Elise fall out really quickly late game. I recommend even a small base damage with a really low ap ratio. Compare the stun to other similar skills like Morg's or Lux's binding. Veig's has no damage but it's an AoE spell that can potentially trap an entire team for 2.5 seconds. Morg's binds for 2.5 seconds as well if I'm correct, and has a huge nuke with good ap ratios as well. Lux can bind 2 people. Brand stuns for 2 seconds and assuming you've been hit before, his skillshot isn't all that different from Elise. Annie stuns for 1.5 seconds, but can do it every 4 hits and can group stun through her W and R. Seeing all this hard cc, I feel like she deserves even a slight base damage on her E, or at least an extension on that stun so it's not just for 1.5 seconds. The animation is slow and fairly easy to dodge as well.
-Or, would it be possible for her spiderling to have a 20-30% slow? Jungling as Elise, it feels like taking an exhaust is almost mandatory because unless you land cocoon and have rappel to exit/close gap, it feels like she doesn't have any options. It's also true of common junglers like amumu, but he has an AoE snare that basically guarantees a kill after lvl 6.
-She also has a really low bonus for her ultimate. What I mean by that is that in spider form, she gains extra armor and magic resist. It's really useful early game during jungling, but 20-30 armor and mr is really kind of ineffective late game. She doesn't have the escape, since most people will use rappel to enter/kill, and considering that her health isn't as high as other assassins (Garen, Rengar) and she isn't as guaranteed an escape (like Kha's ult), she needs either more cc or more durability.
-Lastly, her heal from frenzy seems really low. Even when I build 350-400 ap mid game, I find that I can only heal for 4(+7-8) health per hit on a skill that lasts 3 seconds. Considering her spiderlings (assuming she has four by mid game), she hits 10 times, two for herself and eight for her spiders. That's only 120 health, even less than one red potion.... I know that it was meant to help in jungle sustain, but it almost seems irrelevant.
If my reasoning/math is flawed, please let me know. These are just basic opinions I had of her playing my first 5 games. I've yet to grow used to her skillset so this isn't definite and I realize that giving her everything I asked for would be far too large a buff, but please consider some of these ideas when/if you rebalance her.