Why do Ubers care more about coverage than STAB? In other tiers, even Iron Head is used for STAB, what is different in Mewtwo's Psychic?
Also, are Suicune and Raikou viable in Ubers? Thunder is used alot in Ubers, so why not use the Thunder Pokemon?
Because in Ubers,(*2) is a lot better then (*1.5/2). There is just so much that resists (or is immune in Darkrai's case) to Psychic that it really isn't worth using.
Suicune is completely outclassed by Kyogre, but Raikou might be effective. You should give it a test.