"Mana Hungry" should not be a Lux weakness
She's already completely skill-shot reliant, squishy, slow, unable to deal with tanks, and has bad cooldowns even if she maxes out CDR. I think that's enough drawbacks, so why should "mana hungry" also be among them?
Riot, please lower the cost of Lucent Singularity. It cripples her early-to-mid game far too much, such that she can't even long-range farm against assassins like Zed.