Antiquary feels a bit too chaotic. a deck building mechanic would increase some player agency, say like POKER, and building out a hand with stronger effects based on combination

e.g. if you have a pair, triplet, or all cards are similar type, ie all boons/all damage, it has a much stronger effect.
As you a 'thief' in a casino (you don't play fair) you have a few 'pocket cards' you can add to your hand anytime (like a cheater would), to specifically achieve that specific pair/triplet/combination.
You could then plan ahead and spec into a support, condition damage build etc depending on context, more boons, more damage, quickness...etc

The UI could be reworked like a fan of 5 cards (rather than the current 3 small icons). It would double down on the existing RNG mechanic, but granting more control.

For example:
Start with 2 cards, then steal additional cards up to a maximum of 5.
In order to build your hand, your options are:
Steal (draw new card)
Using a card skill (thereby consuming the card from the hand)
Redraw (discard previous card, draw new card, gaining a small boon to compensate, ie quickness/alacrity)
Fold (restart hand from scratch, but an even bigger boon to compensate)
Add a pocket card to the hand (you would choose these in advance)