Shedinja can work in OU. I have a few variations of a team between Shoddy and Wi-Fi. However, you really do have to build your team around Shedinja. Almost every Pokemon needs to be able to support Shedinja in some way.
You absolutely, without doubt, need one Rapid Spinner and at least one Pokemon to change the weather to something non-damaging. I usually use Rain Dance, and Shedinja could probably be thrown in on any number of Rain Dance teams.
As for a Spinner, I tend to use Tentacruel on my Shedinja teams since he can soak up Toxic Spikes with Liquid Oodze.
The tricky part of Shedinja is getting behind a sub. Most common Baton Pass users share a weakness with Shedinja. Togekiss and Zapdos share a rock weakness, Ninjask shares most of shedinja's weakness, and so on. Ambipom could work, but I tend to use it as a lead and don't want to bring Shedinja out too early. So I usually opt for Vaporeon with Yawn/Sub/Surf/Baton Pass.
I can see how it can do a lot better in UU since Abomasnow is BL and every other perm-weather is either OU or Uber, unless their pre-evolvs are used.
Yeah, Shedinja can work in OU, but it's VERY hard to successfully pull off a sweep, whereas in UU, it's much more plausible. The problem is that Tyranitar (#3 in usage) absolutely destroys Shedinja. If you can't get rid of it before bringing Sheddy out, your main sweeper's toast. Even with a weather changer, if Tar comes in on Sheddy, then you either switch or die. Pursuit hits you on the switch or maybe Tar gets a DD up as you switch to your weather changer, from where he can do some serious damage to your team.