Ice-type Pokemon are usually bad; the Ice type is just a bad type to be. Kyurem has uber-level stats and is OU in two of its formes. Weavile has an offensive build instead of the usual defensive build GameFreak tries to throw at Ice-types, and even then he's UU. Mamoswine is really just an exception.
If there is an Ice-type pseudolegendary, it had better hope the Ice type gets a much-needed rebalancing! --- Creator of Jay's Journey (see quote!) "It's not ten years old! Therefore, it sucks!" - Nostalgia whores everywhere