It certainly looks like the original intent was you would sneak attack an enemy when they cast a spell (neutralising it at high levels), and it was not intended to be used with allied spells. So the original concept was much more mage slayer than mage sidekick. It shows how difficult proof...
That's not exactly true. The Ravnica book sold in line with the other setting books (not as well as Eberron). The others sold from slightly worse (Theros) to very much worse (Stryxhaven).
It was leaked, then quickly removed.
Since you mention canon, have you noticed that the MtG D&D books are treated as non-canon? In the sense that they are never mentioned again in other D&D products. The abortive Lorwyn content is the only one that is connected in any way to the D&D multiverse. If you compare to the Radiant...
The vampire can create more vampires, so it spreads like a contagion, so it could easily have a much higher body count in a city. It's also easier to pass unnoticed. BG3 touches on this.
What I think @Misanthrope Prime is talking about is the Stephen King and his imitators style of American...
Setting aside all the points people have already made about why this is highly unlikely to impact D&D, none of these subclasses suggest “gonzo shenanigans”.
Can you think of a specific MtG setting they would be a good fit for?
My personal view is that we are only likely to get one setting in 2026, and it will be Dark Sun.