About the actual ranking: I actually think I'd probably put Familiar around third. I mean, it's very strong in a vacuum, and it can demand an answer, but... it doesn't really work with much of anything else, a reasonable number of strategies can actually just try to race against it (and will usually win if the opponent misses 3p, lose more often than not but still have a fighting chance if they hit 3p), and there are a lot of cards that counter it - from certain gardens slogs, to most every other curser (in the absence of other good potion-cost cards), to decent trashers (of which there quite often is one). Don't get me wrong, it's good, but...
Scrying Pool basically needs non-terminals. Well, it also needs the absence of fast non-potion stuff sometimes, and it prefers cantrips or trashers and things... well, it's VERY strong, and the best partner for scout, I think I'd put it #2 ahead of familiar and behind...
Vineyards almost just needs any kind of action. It obsoletes provinces so much it's almost funny, and there's actually a number of times where I find myself very tempted to open potion just so I can buy these green cards faster. I mean, winning the split can be huge. Ok, sometimes it's just a hard-to-get little green card (a la Gardens, Silk Road, Feodum), and even here it's kind of okay, but usually it's just a monster. And this is without noting how insane it is with gainers...
Possession probably ought to be higher. I do think that comparing it to province is reasonable (and not at the start of the game, though hey, I am pretty sure you would take a free province buy turn 0 most games - a reasonable approximation is testable by having one player get death cart, wait around until a province hand, trash the other ruins and the death cart with itself, then wait for a clean reshuffle and go, with the other player just passing before this, and assuming that ruins, death cart, or a random 10th kingdom pile aren't relevant to the kingdom otherwise), kind of, and for good swatches of most games, you would rather have possession. I actually think that more than "it's expensive", the problem with it is "it's terminal", and of course most of all "You have to get the second dead card" (potion). But generally, if an engine is possible, possession is good. In a mirror, you get to go nuts with their good hands, which aren't coming until around now anyway. Against BM, they can nuke themselves, sure, but you can just blow by with the engine sans possession there. I mean, you aren't technically getting the possession in this case, but it was a good card for you. I think I might have it at number 5, ahead of Golem even.
University should be ahead of alchemist in my view, but it's not very good. I mean, it's not a very good card to have in terms of being necropolis (though it can be ok sometimes, especially with draw-to-X), and that's a pretty big blow. But besides this, again you have to get a potion, and then you are just faster getting to 5 by going for it more directly, until you're down pretty deep to like the 6th 5-cost or something, beyond the missed opportunities early on. Obviously it's board-dependent, but this is a pretty massive tempo disadvantage.