As Gligurr mentioned, Taunt kills this strategy. Also, you're not thinking correctly with Mimic. You would need to waste a turn to use Entrainment on Audino, because Mimic copies the move and replaces itself with the mimicked move. Meaning Shedinja needs to move first next turn and give Wonder Guard to Audino, and Audino to Eelektross. This would also mean that you must give Shedinja 84 Speed EVs assuming you have 31 Spd EVs in order to outspeed Audino, and Audino must not have any EVs in Speed. If you maxed out Audino's Speed, or made Audino's Speed higher than 196, this will fail. This is very stat reliant. Or else, you must ANOTHER turn to fully carry the strategy out.
This would take many turns to setup, and require extreme team support to carry out. I won't be surprised if someone didn't take out one of the Pokemon. Let's see:
- Turn 1: Eelektross used Magnet Rise, Audino used Entrainment, Shedinja used Mimic, gained Entrainment.
- Turn 2: Shedinja used Entrainment, Audino used Entrainment / Random move.
- Turn 3, if Shedinja does not outspeed: Audino used Entrainment.
By that time, due to Shedinja's frailness, your opponent would have figured out the strategy and wiped the vital part of the strategy out.
Otherwise, this is a pretty common strategy, and is okay for surprising people, I guess.