The main reason that your set was rejected was mainly the item choice. LO is a bad item for all-out attacking Cobalion, because very often he does more damage to himself than to the opponent, cutting dow his lifespan without doing anything significant. But Expert Belt gives almost the same firepower, still ohkoing Blissey after SR, whith no recoil at all, which means that if you play Cobalion right, he will have enough life left to take on the physical threats it is supposed to.
i got a question, why is shift swim with drizzle ban from ou? i don't see the point if chlorophyll is not ban with drought then why is drizzle with shift swim i propose a petition if the rules were that we can have drizzle with one shift swimer per team allowed, i think that is fair,think about it the BW2 metagame needs to have more interesting factors like using the shift swimmers like kabutops or ludicolo, i think it would be more fun to use some of the forgotten pokemon that have potental to sweep and to make the pokemon community fun again to create more strategies