I also don't play AST much anymore so I don't feel 100% confident on it, but the forbidden website believes I mained it in Aspho, likely thanks to P3S and the Macrocosmos Incident. Still, I think pretty similarly in what you see as the 'issues to solve'. Hence my idea in the thread I linked: redistribute the CPM spent on cards to be more evenly spread, and make more use of mini-buffs. Major Arcana would be the 1min 'moment of power' buff, since many classes do still burst at 1min, just not as hard as at 2min (Monk ROF, NIN Trick, RPR Gluttony, SAM refreshing it's DOT, SMN alternating demis, etc). On the flip side, making Minor Arcana use the full deck of sixty (well, 54 since the Majors are part of it) gives us a way to mix up the GCD loop, make it more interactive, and give a lot more focus to the idea of it being 'the buffing healer'. You'd have every 6th GCD on average be using a Minor card on an ally
I wanted to have the Major Arcana be, with current damage/gear values, each contribute around 30k of damage. I did this because I had looked at the current best run of P11S, and looked at the effect of one of the cards used on their SAM for one 2min window. It was 18.5k, multiplying that up so that it's 10% buff instead of 6% would make it roughly 30k. Hence things like 'Bole reflects 10% Max HP as damage, 3 times' would, with current numbers, be about 33k.
Minor Arcana, on the other hand, I'd hope to try and balance to be roughly 300p, as compared to Malefic's 250. Additionally, I wanted to have some level of RNG based on the card's value, but still keep it's impact on the overall damage low, with the majority of the effect being 'guaranteed' (you'll always get 300), and the RNG part being way smaller (being like 5-45p depending on card). I took inspiration from Darkmoon Decks and how their effects are scaled based on 'current top card of deck'. If I had more time/cared about the class more, I'd balance them better/come up with better effects, I feel like the Minor ones are maybe kinda bland in their application, but considering what we're working with at the moment I'd say it's an improvement even as it is
Many say 'separate the utility and the damage since people only ever want the damage, and forgo the utility', but that just leads to a very similar issue. You'll use the damage as part of the rotation, and the utility can't be relied on if it's RNG. If you have RNG between Mit, healing%+ and movespeed+, if you need the mit for a raidwide, you're gambling on getting the right draw at the right time still. So I'd rather just attach damage to the utility, rather than try to seperate them out. There would still be opportunities to use the cards in ways that are 'creative', for example, if Arrow increases AA speed, there's theoretically a way to get PLD an extra Sheltron. NIN could have had the same if they still got gauge from AA but they don't now. If a caster dies, throwing a Ewer would give them the MP, but not the damage effect. But them being OOM is a bigger DPS loss than the effect of the card, so making that a choice creates interesting decision making situations.
If it were completely down to me, I'd make one of the cards be 'you can use a major DPS ability, with no regard for CD or costs', like giving a monk a free TFC, a NIN a free Dream or a GNB a free Blasting Zone. But that'd be 500% unbalanceable