I actually think Moat is the worst in 2p, but not the worst overall since it gets so much better in multiplayer.
Back before I started playing in Isotropic, I thought Secret Chamber was the worst card in the game. And now it's my single highest Effect With, but that took quite a while to happen. If you're a mid-level player (or even a good BM-esque player) it totally makes sense to rank Secret Chamber last, it's primarily an exotic engine helper masquerading as a Moat-that-doesn't-actually-Moat, so it's hard to figure out.