I have played several matches against syrim using an OHKO team. Surprisingly, it is neither completely broken, nor completely worthless.
OHKO moves allow certain Pokemon to win match ups they would never dream of beating otherwise; bulky Roar Scald Kyogre can now run Scald + Sheer Cold, pretty much dominating slower, defensive teams and sand. This is by the virtue of how many turns Kyogre has to use the move against defensive checks to it; Arceus Grass and Latias risk a 30% chance of getting OHKOed each time they come in, and their inability to OHKO Kyogre and temptation to use Recover means that a possible two uses of Sheer Cold will give them a 51% chance to been KOed. Giratina-A and Gastrodon are no longer 'good' checks to this variant of Kyogre, as they are only beat it through residual damage.
However, against offensive teams where there are far less turns, this set does not excel. Kyogre cannot grab too many free turns against teams that aim to end the game within 15-20 turns. Syrim was using an entire team with Pokemon that had at least one OHKO move. He had great matchups against sand where Kyogre dominated the slower defensive checks; rain stall, where taking the turns to set up multiple hazards and phaze things resulted in core members dying off too quickly and backbone collapsing; and offense where he was utterly destroyed, although aided by a large sequence of OHKO moves missing, such a thing is unavoidable when relying on a 30% in the first place.
Now, syrim was obviously testing the extreme of the move for the sake of seeing its effects in practice. However, it is more than viable to have just a few Pokemon, or even one on your team. Bulky Sheer Cold Kyogre used as a standalone set is undoubtedly analysis worthy, and has the potential to support teams in a way that would previously be impossible. Is it broken? I don't think so; its shortcomings are apparent and it will, in practice, almost never sweep an entire team. Is it good? Yes, it definitely has a niche, and makes defensive Kyogre just that 30% scarier.
There are, of course, other Pokemon with access to OHKO moves; Groudon, Gliscor, Lapras, Kabutop, all possess it in one form or another. Thus far, however, I have found bulky Kyogre to be the most threatening due to the vast amount of approaches to checking it being defensive rather than offensive.
Last edited by Poppy; Sep 18th, 2012 at 2:20:01 AM.