Even from my modest play experience, I can say that OHKO is an undesirable element in a competitive metagame. You just press the OHKO button and you either get free kills or you don't. It was dumb playing against these moves and using them. My initial fear has been realized in the Ubers ladder - OHKO connects much too frequently, and the reward drastically outweigh the risk in using this move. Perhaps if there was a side effect such as a 34% recoil for each time you miss then there might be some competitive merit to this move. However as it stands now, it's just brainless ez kills.
Sheer Cold Kyogre is good, but I usually prefer Roar for its consistent utility. What I felt was far more threatening was Mold Breaker Excadrill with Fissure. Excadrill doesn't really have anything better to use, and in exchange it can pretty much kill Ferrothorn, spinblockers, and Groudon on the switch. Fissure just made limiting hazards easy and even more.