Why Elise Used To Be Strong
Elise was extremely strong for the longest time because she used to be able to build tank and do damage. Rito nerfed her damage, rappel range, cocoon stun duration, the width of the cocoon, the speed of the cocoon, spiderlings damage, spiderlings tankiness. Did Elise need to be nerf, yes. Did she need to be nerfed this hard, no. Rito thinks they can compensate by buffing the stun duration and buffing the spiderlings.
The stun duration buff is nice but it's not going to do much for her. Since it's buffing her utility but not her damage. She is a champ that punishes poor positioning but if she has no damage to follow up, she's useless and becomes too reliant on her teammates to come help.
The spiderlings buff does absolutely nothing because they last as long a teemo in a 1v5. They die to everything to quick. So this buff is not even going to be noticeable.
TLDR: Elise's buffs are more utility based, the only reason she was good was because she did a lot of damage. I wouldn't be surprised if people start playing her support due to all the buffs to utility and lack of damage.