I just wanted to brighten your day :(
That moment when you get clipped by the very tip of her Q at max range and you see her ult charging and you're just like https://media.tenor.co/images/b4a774d1ef7d6b6a875f4c9412ffe652/tenor.gif
"An enemy has been slain."
CD refreshes
It doesn't "refresh" the CD. It grants her some modest CD reduction on a kill with it (VERY modest reduction at early levels).
uhm, it stacks. if her ult is level 3, and she kills two people with it, she gets 100% CDR not 50. and if you build CDR and only kill ONE enemy with it, her CD is only 13 seconds. Its got lower coolddown than Lissandra's E lvl 2.
It does NOT stack. The wording of it says that "If she kills an enemy champion with it, a portion of the cooldown is refunded." If she kills an enemy champion then she gets the reward - it doesn't stack.
Even if it did, there are very few situations where her ult kills more than one person.
is that the kdrama meme :3

People never seem to realize these help too
[{quoted}](name=An Enemy Sutando,realm=EUW,application-id=Ir7ZrJjF,discussion-id=gHff2ckg,comment-id=0002,timestamp=2017-04-30T19:06:28.841+0000)
That moment when you get clipped by the very tip of her Q at max range and you see her ult charging and you're just like https://media.tenor.co/images/b4a774d1ef7d6b6a875f4c9412ffe652/tenor.gif
Pfft. Some Lux that ults after landing Q without throwing out an E.
But then you realize that you picked Olaf mid and you just got lv 6 http://i2.kym-cdn.com/photos/images/facebook/000/544/108/8e3.jpg
[{quoted}](name=Lord Galvatron,realm=NA,application-id=Ir7ZrJjF,discussion-id=gHff2ckg,comment-id=0006,timestamp=2017-05-01T00:35:13.725+0000)
But then you realize that you picked Olaf mid and you just got lv 6 http://i2.kym-cdn.com/photos/images/facebook/000/544/108/8e3.jpg
Great. First it's the beef. Then it's the salt. And now it's the pepper. Talk about a food fuck up.
Olaf mid into Lux sounds pretty bad pre 6
You can just farm with Q and E pre-6. Also she's super vulnerable if you land an axe on her when she misses her bind.
DARKNESS!
:^j reasons I play Lux
Its harder to lane against her as talon now with his new E. cant dodge shit like you could before.
Playing anything without free mobility against Lux is just asking to lose lane. Her E is far too strong for being nearly undodgeable.
It's absurdly mana-hungry (20% mana pool at level 1, and the cost rises dramatically with ranks), and while it's early-game bases are barely higher than her Q's (top advantage: 10 damage), the scaling is relatively bad enough that there's barely a difference once she has an amp tome, and none if she puts a second rank in her Q. The size and unit passthrough are the only things her E has going for it. Otherwise, it's just a worse Q with no root.
I recommend you work with a friend to try to practice predicting her E in customs. In lane with boots once you know how it works, it's not hard to juke unless you're right in her face. Most Luxes wait until they land a Q before they use E for that very reason. It's a pain to land, and too expensive to miss. If Lux is spamming her E, focus on juking and live with the satisfaction of knowing that she's going to be out of mana and very, very vulnerable soon.
her E is a reliable poke and waveclear tool.
Late-game, sure, but early-game she has to sacrifice a decent chunk of her burst if she wants to itemize to use it for waveclear more than once in a blue moon. It puts her in the awkward position early-game of needing most ADCs to already be down to ~50-60% HP before she can nuke them to dead. It's not undoable, but it makes ganking significantly harder if you don't have harrass-y side lanes. Other issue is that Morell doesn't use Aether Wisp, so she loses a fair bit of early-game movespeed there, again decreasing her ability to roam.
Support Lux can get away with spamming it a lot more, mind since supports get a ton of mana regen + Lux can't get her big burst items as support anyways. Mid, though, which is where I normally think of her, it dramatically changes her playstyle from a burst mage to a weird sort of snare/harrass mage - kinda like a Morg with a bit more up-front damage but without Morg's amazing W + E. I might build it that way if I'm pretty behind and can't farm well? Otherwise, I find I have a lot more success with a setup designed around using my abilities more sparsely with more effect instead of constructing a whole build around spamming E.
(14/1/9) : The light is fading.