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Maybe 95% vs 5% and sure pass vs. sure gain is a bit too "black and white" as I've had fun stopping an opponent's Minion train with a critical Saboteur every once and a while, but to me it's just a waste of a valuable card slot.
I agree that this is too "black and white." I just finished a game where I was going for a Watchtower-Hamlet-Oasis engine with a Young Witch (Hamlet was Bane). Outpost support. It was pretty sweet. He was going for a Watchtower + Big Money strat with Hamlets thrown in (not for actions, but for +buy/Bane).
It wasn't until several turns in that I realized that his Saboteur was going to destroy me so hard, as many of my components were cheap and I didn't have the luxury to spam silver. I kept at it, though, having to replace YWs, Watchtowers, and my one Gold many times. Even lost a province. However, in the end, I split the provs 4-3 and his two Duchies and 4 estates were countered by the 3 curses that I had managed to slip past his Hamlet-banes/Watchtowers (and my own 3 estates).
I really thought that his Sab purchase was a decent one, I just got the draws needed to close the deal. If anything, I think he should have bought more.
Anyways, all this is to say I think this is a game that fits in that grey area between your 95%-5% "black and white," so I'm glad you included a qualifier there.
I think Sab still has some interesting dimensions that I haven't yet explored. I'm not saying it's the deepest card in Dominion or anything, just that it's not totally bland.
In fact, I think your "Sab is not interesting" argument might even apply to Fishing Village! If you want Villages, it's a no-brainer to buy. If not, also a no-brainer to not buy. Rarely is it much of a debate. Sometimes, but I think in the vast majority not.