Shedinja is a piece of junk. Sandstorms are popular. Spreading burns are popular. Entry Hazards are popular. It dies before it does anything. Do not use thing unless you have one hell of a strategy to use.
Wonder Guard would be awesome. However, Fighting Types have risen to power and are packing Stone Edge and/or a Ghost striking move. Ferrothorn exists, meaning Fire attacks are everywhere. It's also weak to Pursuit, so it can't run. Hitting Shedinja is too easy.
Shedinja is a horrible movepool. It might have Shadow Sneak, but that's really the only good thing.
The worst thing about Shedinja: One HP. Wonder Guard will never bypass the fact that this piece of crap has only one HP. If it is put in a situation where taking damage is guaranteed, you can't save it. Period.
Bottom line is: Shedinja needs so much support that a whole team would revolve around the use of Shedinja, which is suicide.

I will give Shedinja one saving grace: switching into Choice-locked enemies. This gives Shedinja a free switch in. This lets Shedinja scout. This saving grace will not last long though. You have been warned.