After playing a lot with Elise, i notice that she is very strong, and at the same time, very weak, depending very much on the situation. I've thought about her kit, her cooldowns and how does everything work together as a whole, and i think that the best thing would be to change her human form E, instead of changing her damage/sustain, which is already incredibly over the top.
Recently (patch 5.12) riot has made significant changes to her kit, increasing the reliability of her sustain in spider form (passive), and adding the insane damage/healing buff on her spider E. I think this approach isn't really gonna work out well, because it will make her deal ridiculous amounts of damage, while healing a lot, making her an unstoppable duelist, and probably ending up with her getting banned, once people realize her insane potential and star playing her in the top lane.
WHAT I THINK THAT SHOULD BE CHANGED:
Basically, i think that her human form E is the only thing that's wrong with her. It is a rather slow skillshot, that can be blocked by minions, and has a very long cooldown. Even if you managed to hit the stun, you barely have time to turn into spider form and get a couple of autoattacks and a Q in, which isn't really worth it for a skill so hard to hit and such a big cooldown.
I think that the logical solution to this would be one of the following:
1- Make her human E ignore minions (same as leona's blade). Let's be honest, why the fuck would you EVER need to stun a minion, and for barely 1 second??? I understand that this makes it easier for the enemy to hide behind minions and avoid being hit, same as what happens with blitzcrank's or thresh's hooks, or nidalee spears. The thing is, that those skillshots have a significantly lower cooldown than elise's E, and they are much more devastating if being hit by them. The most similar skill to elise's E is leona's E + Q combo, and said combo ignores minions, and on top of that deals damage (while elise's E doesn't). I think it would be pretty fair, and help her when ganking the lanes, because there's nothing more annoying than missing a cocoon because a stupid minion suddenly changed direction and blocked it.
2- Make her E a root instead of a stun, but significantly increase the duration, for example 2 / 2.25 / 2.5 / 2.75 / 3 seconds (like moragana's). I know it seems unfair, but think about this: Lux has a 2 second root that can hit two targets, and morgana a 2-3 second root, and both those skills deal a hefty amount of damage and have similar cooldown to elise's E, while elise's deals 0 damage. On top of that, any of those skills give both of them the chance to pull off a combo and 100-0 you from a safe distance, but human elise doesn't have high enough AP ratios to do that, and instead, she needs to go into spider form and get in melee range to deal most of her damage, which could be risky, because the target will only be rooted, and can fight back at that distance.
3- Similar to the previous idea, but instead of a snare, make it a big slow that fades over time (like a reversed nasus wither).
My favourite ideas are the last two, because i see them as the most fair choice (still easy to dodge), and it suits Elise's playstile and lore better. The idea behind this, is that Elise would feel like a real spider, hindering you with her web making you unable to escape (instead of a shitty web that breaks in barely 1 second), and always trying to force you into a melee duel, (which is how i felt she was meant to be played) but still being fair and not making her OP, by removing the stun and giving you the hability to fight back. Of course, i think that if these changes were made, the steroid on her spider E should probably be nerfed, for her to be really balanced.