I really don't like this change, honestly.
If you check Elise's winrate by what skills she maxes first, you'll notice that when she maxes W first she has a winrate of 44% in Platinum + in the jungle. Well over 50% of all players max W second. However, players that max E second have a 49% winrate at the same ELO, but only 16-18% of players use this skill order. And if you think about it, this makes a lot of sense with how much more you gain from E than W. W is an increase in damage in human form and attack speed in spider form. That's it, No CD reduction and no extra utility. Maxing E second gives you a longer stun on a shorter CD. It also decreases the CD of Rappel AND it increases the damage on your spider autos when you descend on an enemy target by 100% at max rank. You gain so much more from maxing E second, particularly with a tankier Elise build, which right now is more effective.
Now why is the change on the PBE bad? It is going to confuse people more than they are already for one. People are going to think that E is a one point wonder now, but there is so much more tied to E than stun duration. Now this will be a significant buff to her early game, but this is effectively yet ANOTHER nerf to her mid-lategame. You have less effective Stun time over the course of the CD on E with this change; 2/10 vs 1.5/8 with no CDR and 2/6 vs 1.5/4.8 at max CDR. It is minor, but the issue is that more people are going to forgo maxing E second and it is her major contribution in mid-late game teamfights.
Reason number 2. This has the potential to make her early game too strong. 1 second vs 1.5 seconds doesn't seem like much, but it is huge in the early parts of the game. An extra half second is extremely strong on someone with Elise's 100-0 potential in the early game. I am extremely afraid that this is going to lead to her receiving more nerfs as a result of her oppressive early game. She already falls off faster than Lee Sin, I really was hoping that they would target things that would help her transition past the early game, rather than completely front loading her entire being into the first 12 minutes of the game and then letting her suffer throughout the next 20 minutes.
So the best skill order is probably going to finally be what everybody is doing already. Q-->W-->E; though this is still debatable. I think Riot was trying to encourage people to max E second in the last patch when they added the bonus damage on her Spider E, but when nobody caught on that maxing E second was stronger, they decided that it was better to buff the skill order that most people are using.
Overall, I think this whole Elise event has been handled very poorly by Riot. They waited too long before doing anything about Elise, and when they finally did, it was at the worst possible time. With a new jungle item that they thought would be a buff to her, and with AP itemization changes just around the corner, they tried buffing Elise by boosting her sustain and giving her more incentive to max E second. Because it had been such a long time since Elise had been played with much frequency, her skill cap is relatively high when compared to the tank junglers dominating the meta, players trying out the possibly underpowered Runeglaive on her, and a last minute reduction in her sustain before the patch went live, her winrate went down after her "buffs" (just to be clear, her E change was a legitimate buff, but people weren't utilizing it as they were still maxing W before E; her sustain change, however, was not a real buff).
Now the AP itemization changes (Liandry's in particular) are about to be live, the rework of a jungler item in the Sated Devourer upgrade, and buffs on the PBE to her already strong early game are dangerous in that she might end up dominating as she will be unrivaled in the early game versus an influx of farm heavy junglers using Devourer. If the worst happens Elise might end up getting nerfed again. I honestly don't think this will be the case, but it's a worst case scenario that I am afraid of.
That's my rant. It's a little much to read, but if you do, I would appreciate it. I don't feel like the buff on the PBE is the right way to go, but we'll see what happens. Peace.