Hm, from the aspect of her kit I feel you're incredibly reliant on her stun to chain together a killing combo, but I'm okay with that. It feels very rewarding to pull the combo off. Her cocoon buffs should also make her even more difficult to juke, so I'd almost rather wait for that buff to settle than decide if she needs more to aid her chase and overdo it.
If more buffs are in need for that aspect of the champion, I wouldn't actually want them to give her more range on her Q dash forward because that would make her just another irritatingly mobile character, but I feel her Rappel could reward you better as a gap closing tool when your stun fails you. Most of the time you drop down and just sit there while the enemy has a chance to waltz out of your range. There are a variety of ways it could be improved that would have different effects on her overall strengths and weaknesses.
-It could make her drop down behind the enemy, which would allow you to account for the extra movement away from you, but potentially make it a higher risk move to use than it already is.
-It could apply a small single-target slow on the unit she targets(The AoE slow proposal I feel is just too much utility).
-You could make it do damage instead of increasing its reliability, slightly amplifying the damage of her total spider form combo when done successfully. (actually adding the above effect as well if you itemize into Rylai's. Could potentially make the item too strong on her. You could avoid this by making it an on-hit effect I suppose.)
-You could also allow Elise to start moving while she's dropping down from Rappel and avoid the movement lockup.Might take a bit more work on the mechanical side, I don't know.
Currently I do feel Elise's role is more of a carry amplifier and she doesn't do a whole lot for herself. She can't full combo anyone to death, but she also doesn't straight up duel well with just about anyone. There are a number of champions she can dispatch fairly well on her own, but if they know the limits of your damage they can pretty easily predict your initiate. If you fail to pull everything off effectively even the champions you can handle may turn around and kite/burst you to death.
I am content right now with waiting for the full effect of her upcoming slew of minor buffs to settle, but Rappel is definitely the skill I would target for some quality changes.