It'd be decently "smooth" at least, with just a few changes, but that'd likely still leave it far from compelling to most former AST veterans.
For me, the largest issues are that Divination's CD seems to exist only either to ensure AST has the least rDPS (as some sort of revenge or reset of former bias favoring AST that can be tuned back to balance once WHM has had its time to shine) or to allow for Minor Arcana, and that Seals are made clunky at best -- superfluous at worst -- by the CD, the scant percentile rewards, and how the Seals themselves are replaced.
Note:The shallow but relatively effective fixes, then:At present, 6% of the 15 seconds of a level 70 BLM's Astral Fire phase (ideal damage outside of including Foul or Thundercloud) is only worth a raw (i.e. after Magick and Mend, Astral Fire, and the then-10% Enochian multipliers multiplicatively affecting each other) 306 potency. A single Malefic III GCD saved is worth nearly as much. The amount provided is... pretty negligible. If, say, Lord of Crowns were still a direct damage option at even just 230 potency (therefore 299 raw potency after Magick and Mend), it would be only 7 potency less than near-perfect use on the near-perfect target, which would mean that most of the time, you'd rather consume cards via a pathetic 230-potency oGCD attack than hand out cards to others if not for contribution towards Divination.
- Redraw can no longer draw the same card(s) as have already been drawn within the same Draw period. Think of it as drawing a new card from the deck of only 6 without returning and shuffling the old one (in)to the deck.
- Change Divination to a 3-minute CD of 6%, but have each unique seal decrease its cooldown by 30 seconds. Thus, it is available for immediate burst, but you could also potentially reuse it every 90 seconds if RNG favors you. You are no longer obliged to use one Minor Arcana per Divination.
- Rather than simply replacing the last Seal regardless of benefit or disbenefit, new Seals will now always replace a non-unique Seal if present. Thus, a trade is always beneficial.
- Minor Arcana now converts an existing Seal into the seal of crowns, but cannot newly create a Seal of its own -- only convert or "King/Queen" an existing Seal.
- Return Minor Arcana into direct potency. Healing for Lady. Damage for Lord. Something in the range of 440/600 potency of healing (a single Malefic IV saved is worth 240 potency) or 220/260 potency of damage (so, 286/338 raw potency). These would thus be stronger, on average, than a typical card, at their given levels, but would not contribute seals. They are, effectively, discounted if you had bad RNG luck between your third draw and Divination use, since they can replace but cannot create a Seal.
In truth, though, I'd much rather have back the old cards with simple balancing changes and system improvements. I don't mind Divination itself, but Horoscope and Celestial Intersection seem poor oGCD-replacements for the complexity and power previously granted TD and RR.
(On the other hand, I don't actually mind CO no longer extending buffs, especially those affecting myself (like LD and LS, which had to be included into every CO), not because I disliked Time Mage aspects (I love them, actually), but because its implementation just made everything feel locked into sets if used optimally. That just made me feel obliged to stack all my power into brief windows and then just wallow in boredom until the next burst, as if I was an AST only insofar as I could stick as many skills as possible together so that I wouldn't waste any output from a skill that wasn't particularly fun to press anyways, rather than how well I could manipulate AST- or Time Mage-ish things.)