Magnezone still holds better coverage against the likes of Scizor and Ferrothorn with HP Fire. And if you get Tricked say good bye to your bulk on Porygon2.
Everybody will think to do it. If the Pokemon relies on an item to be useful and your opponent runs Trick then don't you think they'll be smart enough to use it on said Pokemon?
The only Trick users I know are Rotoms. I don't remember others, and those usually attack me instead of Tricking me. And one time I Traced Magic Mirror. God, that was fun.
Trick is also run on the likes of Jirachi, Latias and Latios. I think a great way to screw someone over is by using a pokemon with Klutz ability and giving it a hold item like Choice Scarf. Since Klutz makes the pokemon unable to use hold items it won't suffer choice lock.
Except there are no Pokemon in OU worth using, and even if you did use one, they have better abilities. Running Klutz just to mess with Trick users is too situational to be worth it.