I’m going to go out on a limb here and say “not.”
Shedinja is weird, and there are a lot of Pokémon (or, at the very least, a lot of movesets) that will auto-lose to it, one-on-one. On the other hand, anything that can harm Shedinja, at all, is game over. It’s very all-or-nothing, and since it doesn’t look like Stealth Rock is going to stop being a thing any time soon, the burden is normally going to be on Shedinja’s trainer to keep things from tipping over to “nothing.” The fact that Shedinja can be insta-killed by five different attack types certainly hurts it, but the fact that it can also be insta-killed by burns, poison, entry hazards, weather damage, Leech Seed, Rough Skin recoil, a variety of Tricked items, and anything with Mold Breaker is at least as big a problem (and none of those things are really unusual). Ultimately, almost any Pokémon in the game can learn Toxic – and let’s not forget that Shedinja isn’t actually a top-tier offensive threat in its own right, either (it’s all but certain that, even with direct damage immunity, the vast majority of teams would have something to kill a Shedinja, so it can’t just rely on its invulnerability to wear everything down – it has limited time in play with which to contribute to the team, and Shedinja’s movepool isn’t great). Don’t get me wrong, Shedinja would be a lot more powerful if it just had flat-out immunity to direct damage, but without having a playtest for it, I still think we’d be looking at “interesting” rather than “broken.”
Pokémaniacal 