Vacuum Cleaner in D-tier is certifiably insane. I've been gathering data as I play the game, and based on cards that show up the most in winning decks, it gives me:
S-Tier
A deck: Sailor, Vendor, Butler
B deck: UFO, Clairvoyant, Necromancer
C deck: Illusionist, Vacuum Cleaner
A-Tier
A deck: AI, Stable Boy
B deck: Cowboy, Rubber Duck, Band, Mascot
C deck: Sci-Fi Geek, Villain, Bumper Car, Vampire
B-Tier
A deck: Skeleton, Hermit, Juggler
B deck: Pyrotechnician, Dog, Ghost, Mime, Bat
C deck: Champion, Submarine, Prince, Hologram
C-Tier
A deck: Make-Up Artist, Gangster, Pony
B deck: Shark, Cook, Sorcerer, Teenager, Alien, Clones, Horse, Lion
C deck: Fan-Bus, Teddy Bear
D-Tier
A deck: Spider, Talent, Cow, Treasure
B deck: Navigator, Knight, Comic Character; Lifeguard, Blacksmith, Director
C deck: Siren, Slime, Heroine, T-Rex, Werewolf, Bard, Kraken, Dragon
F-Tier
A deck: Jester, Cat, Shapeshifter, Movie Star, Parrot, Pig, Merman, Clown, Reporter
Rescue Pod not rated because the measure of showing up in final decks doesn't really apply to it. I'd say it's C-Tier personally. I'd say Shapeshifter is better than F-Tier as well, in fact it's kinda because of Shapeshifter that Sci-Fi Geek is so good.
I'll also say that this method overrates starting cards significantly, especially Champion, which I basically never pick but does show up in winning decks just by virtue of just never being cut. As for no B or C cards being in F-Tier, I actually think that's right. The worse cards there are still fine in multiples (or alone for the C-deck vanillas) - not great but not actual fails.
Based on my data, there'd be an argument that UFO and Clairvoyant are on a tier on their own. I sadly did not consign the number of games, but it's north of 500, and they've respectively shown up (meaning at least one copy) in a winning deck 119 and 118 times. Next best is sailor at 105.