Lux is played exactly like Xerath now
With luden's, arcane comet, manaflow band and smaller things ike scorch or cheap shot, all she does is stay back and poke you to death with high damage high cc spells, never really running out of mana
How is that any different from Xerath, and why doesn't he get a 400 hp shield?
Remember when Lux had to weave autos between spellcasts and use the shield purely for trading with other ranged champions?
The same free damage from items & runes is also the reason Soraka is being pushed more and more into the lane bully role, rather than the "help every ally with free, low-power sustain" role.