It seems amazing to me that anyone would call Aven Mindcensor undercosted. He costs three mana. Three! If they spend one (or less) mana to kill it, that's an incredibly huge tempo swing. Knight is the same thing except much harder to kill and has a huge body. How big is Mindcensor again? Oh right, he's a Coral fucking Eel. He's actually worse than Glowrider because Glowrider actually stops combo from going off most of the time, and has synergy with the rest of the deck, especially played next to Thalia.
And that's assuming you want something just against combo. Hell, he's worse than
Mana Tithe for that, which again combos with other cards in your deck and hits every other deck beyond trying to occasionally dead a fetchland (with middling success; I know I've found a relevant land in my top four probably at least half the time I've played against people running this guy.)