Mind Shatter is a card, yes? I gather that this is not the same card. Got that.
The hardest part about gauging if a card is too powerful for Legacy is the fact that the game (and especially Legacy) has crept in power over the last 16 years or so. We have not seen
Mind Twist outside of Vintage in quite some time, so we are stuck guessing at this issue. The last time this card was legal outside of Vintage there was no such thing as Standard (or Type 2). There was not even a Vintage, actually. It has never been legal in Legacy, so we are really in the dark. Speaking of which, it went on the restricted list just before The Dark was printed - about a million expansions ago.
But Mind Shatter has been around for years now with several printings. Forget Legacy for a moment. Modern and even Standard has never found this card to be broken or even valuable. It is a junk rare. Considering how much longer games go and how much more common high mana spells are in Standard, there should be
some evidence on this even with the extra black. It is not as splashable, but has there really been not a single tournament deck since Morningtide that can use a slightly reduced version of a super card? The only deck discussion I found was for a deck that was named for the card, and
they took the card out.
How often does anyone tap four mana on their main phase for a spell these days? Four mana spells in Legacy are game breakers. The bar is so high that they have to be. If my opponent is going to tap 4 mana on their main phase to cast a spell, I kinda expect it to wreck me. (It had better because if I Daze it, that player is screwed.) I think I am pretty relieved if that spell is Mind Twist though. It could have been Jace, Natural Order, or Entreat the Angels. At four mana, this is what you are comparing it to. These are all superior effects, great topdecks, and already in use. Mind Twist is better than all of these? Really?
Even in Vintage, Mind Twist is really only scary when it follows
Mana Drain.
The card is tame, folks. I challenge anyone here to break it.