I like these ideas, but I don't think they'll be able to actually get rid of cards. We'll still need six (due to the lore and due to the way the class quests are structured).

We need to go more towards "every card at least does something to every potential target, even if it's not optimal". That way you're rewarded for playing the right card on the right member but not penalized as harshly for RNG being RNG.

My proposals:

Balance, Bole, Arrow - kept the same

Ewer: Combines current Spire and Ewer to give 20% TP/MP Cost Reduction. If this is too weak compared to new Spire, add a 10% healing buff.

Spire: New Spire grants 10% increased TP/MP Restoration including TP gen on autoattacks, Bard songs/MCN turrets and refresh ticks (but doesn't restore TP/MP in and of itself)

Spear: Stays 20% cooldown reduction, but applies to abilities already on cooldown when the card hits. This makes it easier to coordinate and use.

That way we keep two "resource-related" cards, but make them easier to use regardless of the party composition.