Q? Why are you complaining about Q auto, you should be complaining about E auto (which is actually difficult to dodge/out trade and is reasonably safe).
Anyway, I can't really see her burst as being disgusting. There are SO many ways to deal with her burst; Maw, QSS, Zhonyas, even Abyssal or RoA will keep you from being 100-0ed for most of the game. What I CAN see as being too strong is her saftey; she IS extremely difficult to catch.
Also, even given her Ultimate, Lux's waveclear is actually pretty meh. 2 Es won't even necessarily clear the wave, which means you HAVE to use ult to clear it. This is judged on a different standard from Rumble, because Rumble is not an immobile mage. It's a significant portion of a mid laner's job description to be able to clear waves; champions that can't clear waves tend to do pretty poorly in mid (thus, why Kassadin and similar assassins have bad win rates except when they're overtuned).
For these reasons, I don't see a nerf to Lux's Ult CD as being the correct nerf for her. The two nerfs that I think would be the correct ones to go for would be:
Q: Light Binding
Snare Duration 2 => 1.6/1.7/1.8/1.9/2.0
And/ Or:
E: Lucent Singularity:
Slow : 20 / 24 / 28 / 32 / 36% => 18 / 21 / 24 / 27 / 30%
Something like this. Lux is probably too safe since the change to her Q, which is likely the cause of these problems. She will still be the safest poke/catch mid laner, but not by quite the same margin. She'll also be the most defensive/ team oriented of the poke/catch mid laners due to her CC and shield. She won't have the best waveclear, and she won't have the best damage. Xerath and Ziggs both outclass her in both categories. Xerath can Q+W to clear waves; Lux always has to at least E E, and often has to E E Q auto. Ziggs of course can E Q Q, and his ult can clear even massive waves on its own (where Lux can only clear a normal sized wave with hers.
TL;DR I feel Lux's CC, not her waveclear, should be nerfed.