Figured I’d share my opinion here. I don’t necessarily think Shan is the best (marsh is my personal favorite) but she’s a surprisingly effective character. If you use her right, you can buy basically any card on the market.
The best strat I’ve found is to use her to buy allies and cards like dominate/house war. Try to survive until then and then sweep the game.
Also aggressively eliminate cards so you’re pulling the same overpowered cards every round.
Buy Atium cards like ruin, preservation, and confrontation so you functionally get an extra burn every time you pull one. Then when you get to tier 3, damage output is insane cause you don’t have to rely on tokens to proc the atium burn benefits.