Well, to be fair, Forager doesn't just trash, it also gives +Buy and $ later in the game, whereas Lookout is only a trasher (well, with maybe a small amount of sifting). Also, tracking your deck isn't always the solution to problems with Lookout, sometimes you just get unlucky if you play it near the top of a shuffle (but you still should, because thinning is winning). It's a pretty decent card but it shouldn't be much higher. Having said that, I actually do have it higher, I just noticed, on place 19 instead of 20! Close call though. (Forager is on 13)
Also, Watchtower is a good card. It may very well be the second best defensive card in the game (after Champion), countering cursers and handsize attacks like there's no tomorrow, but it's also the best card for draw-to-X engines. They're sometimes a bit more difficult to build than standard Village-Smithy type engines, but it definitely pays off.
You make a good case for Dungeon > Warehouse (I had Dungeon just 1 place over Warehouse, the difference is probably bigger than that tbh), but top 10 is likely too high. I do agree with your point about Menagerie, it probably shouldn't be in the top 10, it's a bit too situational for that.