Ice block should be legendary and/or undiscoverable. More than 2 is a pain in the ass
I think it is unintuitive to just not have certain cards show up in the discover pool, but one thing I have always thought is that cards should not be able to discover themselves or other cards that can generate infinite value. Kabal courier, glyph, etc should at the very least not be able to discover themselves, even if they can discover other discovers.