"It also kind of has a Tarmogoyf effect, right -- there's a lot of Blue dudes that aren't even worth thinking about now because they don't have protection from target player. Goyf continues to keep a lot of really awesome creatures - not just Green creatures, but creatures period - out of both Vintage and Legacy."
This is not all downside. As the herd flocks to a new standard, some very good but slightly different cards might be easier to pick up. For example, if Legacy flocks to Nemesis en masse, then maybe Clique will drop in price.
Well maybe? But at that point, that's just settling for an arguably 'worse' card. People used to say "Tarmogoyf is good, sure, but Wild Mongrel is
fine." Fine means losing when you didn't have to.
This all operates on the assumption that True-Name Nemesis can prove itself to actually *be* that Tarmogoyf - that Blue creature that says "You Must Be This Tall To Sleeve Up", the stick against which all other Blue creatures are consistently measured. These things have happened before, no doubt - Morphling was one of like, five relevant creatures at one point, slight exaggeration but you know what I'm saying. So if TNN is the Blue Goyf, what's the reasoning behind investing in Vendilion Clique? TNN pushes it out of playability (for the purpose of this argument), it's just a less-good card now.