That's a good approach that works when everyone is at the same level. However, comicbook RPGs have always had the scaling problem of 'what if a street-level hero meets a cosmic-level villain?' The answer, of course, is: 'don't be dumb and do that, GM!' But in games attached to strong IP, like the Marvel Multiverse Roleplay Game, it's always a danger.
That's kind of the point. The scaling problem goes away when you don't have an exterior reference. The die types are not fixed in the rules to specific known measures. They are simply "chance of success".
Batman normally runs around in Gotham, mucking about with Penguin's goons and the Riddler. But, when he steps up to work with Superman, he isn't suddenly overwhelmed. He just continues to succeed because the die types aren't changed.
In effect, the game pushes the scaling out of the rules, and into the narrative description.
This is backed up by how the game handles character stats. D&D, has Str, Dex, Con, Int, Wis, Cha. Most other games have some similar shared set that defines a character. And then you can compare - Jimmy Olsen has a Strength stat, Superman has a Strength stat, and you can directly compare them on a scale.
This game does not have that shared set of stats across all characters. Each character has their own set of Powers and Qualities that define them, so that you generally can't directly compare.