I don't know - I personally kind of like that there isn't any "good" caster mediums or heavy armors aside from two of the three druid-centric armors.
It helps keep a trade-off existing in building a "tankier" caster -- you trade bonuses to your attack rolls and save DC's for your spells for getting to wear heavier armors and benefit from their unique passives and being able to "dump" Dexterity.
I think the caster-based armors should primarily stay in Clothing category and force casters that want those to have to rely on Dexterity + Mage Armor to keep their AC's high.
