The problem is that in current EW design, fights are designed around each class having not only X amount of mit, but X amount of predictable mit. If you make the cards all utility, it doesn't matter what they do bc you can't plan around them. They just end up being cute little bonuses on a static healplan. If you make them all damage, then all cards are useful even if they're boring, and each one has to be played. If you make them a mix of both damage and utility... well, the utility cards will be for lack of a better term 'fucking useless' because you can't rely on them, and drawing one of them means not drawing a dps card. This was well and good with how the rest of the game functioned back in stormblood, but nowadays that's impossible to balance. (It was impossible to balance back then too, they just cared less). Minor arcana is a terrible enough button as it is, and I think people who look at StB with rose tinted glasses don't realize that minor arcana is essentially the distilled version of the stormblood card system in its essence. You either drew damage, or you drew not damage. Yeah you could do some funky stuff with royal road but at the end of the day you basically just wanted to aoe the balance as much as possible because relying on RNG utility to handle incoming damage meant either playing like you're never going to draw the bole, or getting used to dying. A lot.
Like idk about you but I'd rather each card do something I can rely on (doing more damage), with variance on where those cards go and in what order than having to roll the dice on whether or not I'm rolling my eyes and pressing undraw on my third ewer. If you understand why haste in this game is an issue, you should understand why RNG utility is also an issue.
Because then AST becomes highly volatile in terms of how much it actually contributes to specific comps, and they are trying to avoid more situations where one class is excluded due to how niche it is. Haste fucks over how a lot of jobs play. Shorter cast times is literally only relevant for exactly black mage. Reflective damage is a dead card 90% of the time. Double cast is again, highly comp restrictive. You might think flat % is boring, but short of adding crit or DH buffs to the mix it's really the only thing that actually functions without feeling like absolute ass to draw sometimes. You might want crazy, wild effects, but I want cards that I don't have to toss in the trash half the time. I still want to have to think about where I'm putting them, but I don't want that thought to amount to 'oh, this card is worthless. Cool.' And if they add in utility cards, they need to strip a lot of AST's kit or it'll be overloaded and the cards will be pointless half the time. And if they do that, it'll mean that if it doesn't draw the right cards it's just an ineffective healer. DPS cards always do something. % DPS cards are always relevant. You can't have super inconsistent jobs anymore, not with how tight everything is. And if AST is inconsistent as hell and the other jobs aren't, then AST is just playing dice with your odds of clearing any content harder than an extreme. Or every fight is made easier just to account for it.
Also, if you can substitute lady for opposition, why not just use opposition? Now oppo is just sitting there, bc I'm hoping you would plan around the next raidwide as if you didn't draw lady here. All lady is, and all it would ever be, is just... an extra 400 potency overheal on top of what you were already doing. Maybe it could replace a helios, yeah, but I'm gonna be real I can't remember the last time I pressed helios in literally any content and I do ultimates and criterion.