Insane? She has the poorest dps of pretty much any mid mage.
Let's compare the main damage / aoe spells of other mages with Lux's E. It's easy to see that Lux E has the lowest damage while having the highest mana cost and highest cooldown of any similar waveclear on a mage midlaner.
10s cooldown at all ranks, at rank 5 has 240 base damage and 60% AP scaling.
Compare to, say, Orianna W with a 9s cooldown, 250 base damage and 70% AP scaling (plus moving her ball into position to cast it does damage as well).
Syndra Q, with a 4s cooldown, at rank 5 has 264.5 base and 69.5% AP scaling.
Xerath Q has a 5s cooldown, 240 base, and 75% AP scaling.
Ziggs Q has a 4s cooldown, 255 base, and 65% AP scaling.
Viktor Q has a 9s cooldown, 250 base, and 70% AP scaling. With evolution, it has 350 base and 98% AP scaling.
Ahri Q has a 7s cooldown, 280 base, and 70% AP scaling, with half of that being true damage.
Obviously these are not 1-to-1 comparisons, but even so it's not hard to argue that Lux's E falls far short of the other abilities. The longest cooldown of any ability here, sometimes by 2x or 2.5x, equal or worse base damage in every case, worse AP scaling in every case, and higher mana cost in every case. 90% of the time the slow utility is moot because you detonate it immediately anyway if you don't want the opponent to just walk out of it. The other advantages are just so few considering all the disadvantages.
So no, Lux has next to 0 sustained damage to speak of. And especially since tanks are coming back into the meta, she's going to be even worse off.
And as for her shield, iirc, her W is the ONLY shield in the ENTIRE GAME that can't be cast while moving. Which makes no sense because it's the only skillshot shield. If you're trying to hit a moving ally, why wouldn't you be able to at least move with them?