I like where you're going with it, but I'm not certain on the added Lord/Lady effects. I think they would be better as Shield/Regen effects, or maybe grant an effect dependent on Seal, but it still stores the seal. The other problem is, or at least for me, that we don't have a way to take Seals back out if there are multiples of the same Seal. It "shouldn't happen" I grant you, but, sometimes, things happen. You didn't exactly issue the clunkiness of the current system (you have to target a character to buff them), but you did make it less vital to target a character which, I suppose, is good. This makes Sleeve Draw less cumbersome to deal with as you basically use that to bank Seals for Divination while using actual draws for buffs.

In short: Like the idea. Like the MP recovery tied to Lord/Lady. Still think Lord/Lady effects need work. This could tie into an idea I had before of making the cards utility only, but putting the utility into Lord/Lady cards I think works better. My idea was:

Sun Seal: Heal/Regen

Moon Seal: Heal + shield = heal

Celestial Seal: Heal + incoming damage reduction

I think also granting MP regen to it would be nice. Lord and Lady could also determine if it's a single-target effect or AoE effect, but you might have to split Minor Arcana into two buttons in that case.