For those who do not know, early on, Mageseeker Inciter and Mageseeker Pursuader had an on play effect that would give them Power or Health based on the cost of Spell you discarded while playing them. They didn't really see play, they weren't really viable, and most people don't find discarding their more interesting spells to buff a vanilla unit fun, so they were reworked to what we see today.

Interestingly, Sion encourages similar lines of play to old Mageseekers, rewarding players for discarding units with high power (instead of spells with high costs). I think the main differentiation here is not the card that benefits from the discarding, but the cards that synergize with being discarded.

In Noxus, you are happy discarding your Lost Souls and Fallen riders, as it unlocks other cards for you. I now feel like this was a real missed opportunity for the Mageseeker archetype. Imagine if [[For Demacia!]] (or other high cost Demacia cards) had an additional effect like; "When discarded, make a Prismatic Barrier in hand" (other balancing would maybe be needed to keep the card in line). Suddenly you are happy discarding your spells to buff your units, and get a their discard bonus prize. This would revive the Demacia Piltover (other discard effects) pairing that Lux was intended to have and I think it would be more interesting than the current "play a 6 cost spell once" archetype.

You could even make Lux a proper champion, giving a level up condition that isn't just the same as her value engine post levelling up, something like: "You have played or discarded 20 mana worth of spells this game." (again, possibly with some other balance tweaks)