Well, I was already planing to say I think Dame Natalie is underrated. I guess the silly thing there is that I'd only really want her to move 1 place anyways. 2 cards, a Necropolis, discarder, cantrip, trashing...those are all things that might be worse than "gain a card costing up to three," but I think it's more common for that gaining to be better than a terminal Silver.
I've had some good games w/ Natalie, one was really fun w/ Training and Merchant. But it's pretty common for a card that you basically always want in bulk to appear that Natalie can gain. Merchant, Harbinger, cheap Villages, Wishing Well, Pearl Diver, Vagrant, Patrician, etc. And it's a Knights board obviously, so more Lighthouses, and possibly Moats, is better. Speaking of Knights, she gains cheaper cards that can be trashed, reducing your odds of having good cards trashed. This is especially useful if you lose the knights split(not that all or any of them always get bought, but still.) And if you assume that there're enough actions, there are even more cheap cards you'd want a lot of. Like Vassal, and terminal draw(maybe, at least something like Courtyard.) It's pretty cheap gaining, but cost reducers can make it very strong. And even if she's not close to the top of the pile, if there are cost reducers knights are extra likely to be bought.
Feodum makes gaining a Silver better, and Estates can be worth gaining too. For instance, emptying the Estates so opponents can't cash in on Wild Hunt, or if you have Groundskeeper(s) in play. Triumph, Inheritance, maybe even Baron or Island(as reasons to gain Estates w/ Natalie.) I guess a few other things, the cheap gaining can help some w/ Fountain, or w/ Aqueduct moving a vp token from Silvers to better a victory buy. Avoid Embargoes, possibly even Tax. Keep. Some synergy w/ Throne Room variants if there are cheap cantrips. Lots of small stuff, but compare that to a terminal Silver. That just doesn't seem very impressive. I'd(tentatively) agree Sylvia>Vander, but that's about it. 2 coin isn't that much, and it might very well be more than enough(yay! 10 and 1 buy...) or not enough anyways(7...well I was just gonna get a Lab anyways. Didn't really need Sylvia after all!) If you are consistently drawing your deck, then gaining Silvers would be better.
Anyways, that's all I had for knights. A lot of people seem to question the rankings for landmarks, me too. Tomb and Wolf Den definitely seem more important than Bandit Fort or Fountain most of the time. Palace can be a lot of setup for not that much. I mean often you'll want the Golds, and maybe the Silvers, anyways, but generally all the ones that start w/ 6 per player like Battlefield and Labyrinth seem more important. Speaking of Labyrinth, how is that last? It can be really nice since you generally want to gain more than 1 card a turn anyways, and the person who starts doing that first can gain an advantage. Baths should be last imo. It's rarely important, and really is just small help for dud turns. Tower seems oddly high. Emptying a pile is easy enough(depends what pile:) ) but you need a lot more than your opponent to get a significant vp swing, and that's just not practical much of the time. Only other thing is I agree w/ people who say Mountain Pass isn't that good.