Something I noticed from time to time in my battles was that occasionally my opponents would lead with something, whilst I lead with Kyogre. If what they had out wouldn't do too much to it and wasn't a suicide lead, then they would switch to a counter. Upon seeing Sheer Cold miss (if it missed, mind you) they would immediately switch into something expendable that can damage Kyogre a bit if they lacked something with Sturdy. If my Kyogre had a moveset for something other than testing how often the move hit, then it could easily take advantage of that. Palkia is suddenly a lot less threatening when you've boosted a bit because they were afraid Sheer Cold's 1/3 chance of hitting it would take down something before they got an attack off. What if you were using a Choice Scarf? Unless they had a scarf, then they could fall without even hitting Kyogre. Even if they did, then there's still a chance that Sheer Cold would hit without Kyogre falling to a counter. Alternatively, I could just outright kill the OHKO fodder with a different attack. After all, why should I waste PP on something that was simply brought in as death fodder despite potentially being at 100% HP? Switching back to the counter anyway as a feint still leads the risk of using an OHKO move anyway and KOing the counter. This is disregarding the presence of hazards, by the way.
There's also the matter of boosting sweepers. Unless they have a sub up (which would require them putting up themselves to make it worthwhile) then they'll just fall to the OHKO move. Even then, what if the sweeper is slower for whatever reason? There's a chance that it'll fall because it couldn't create another substitute in time. There's also the matter of restricting it to three moves instead of four because it has to watch out for the OHKO move. Two moves if it's a boosting sweeper. While some Pokemon can pull this off, it also limits their capabilities. With a Kyogre, does it use BoltBeam, or does it pass up some coverage for a rain-boosted attack? Does it pass up a move for Rest? If so, what will you do so those three turns aren't free turns for your opponent? What if the OHKO move hits twice during those turns? Walls could become a liability if they lack Substitute.
On the subject of walls, stall teams would degrade by quite a bit. Since they rely on indirect damage to punch through teams, wouldn't it be bad if, say, you phazed their spinner in? If you aren't using a Giratina(-O) then what will you do? Will you switch your Giratina in to prevent a use of Rapid Spin, or would you phaze your opponent out in case they switched to Kyogre predicting that you'd go to your Giratina? Granted, this isn't new stuff, but if you get the prediction wrong and go to Giratina, then there's a 1/3 chance that it'll fall regardless of HP because of Sheer Cold. Fissure if it's not Giratina-O.
Of course, the third part hasn't been tested by me. I haven't faced stall with a real team since this testing happened. However, the first and second happened. Some people were too frightened by the move, and others were too cocky with the move. It sounds completely broken, right? Well, go on the ladder and see for yourself. So few people use it that it hardly matters. It's broken in theory, but it's different in practice. I see it as something that'll be used mostly by noobs or as a desperation move. Something tells me that this post has been floating around in terms of topic.