Some things to consider
1) The way things were worded, it seems like only cards in Expanded are going to be banned, which
could mean that some things would be Standard legal but not Expanded legal
but probably not.
2) As it is possible the first ban list will coincide with rotation, the preceding isn't foolproof anyway; they could ban something in Expanded while rotation takes it out of Standard.
3)
Broken is not binary. I get it; lots of definitions for this word, many that are completely incompatible, but try plugging in some intentionally broken ideas into your definition, and see if it works. That's how I realized that not only can a card be broken but have a counter available to it, but that broken card doesn't even have to be worth playing at the moment. How? Imagine two
Victini cards. They have the same name, so each copy of one means you cannot use another. Both have an Ability that triggers when you play them to your Bench from hand during your turn. On one, the Ability allows you to take a Prize. The other allows you to take two Prizes. Both are broken, but unless you lack the second version, or we get a format where it is almost impossible to pull off the Ability, everyone's running that second version.
4) How much does it wreck the rest of the card pool for competitive, constructed play? Sure, we can find a use for cards in Limited, as well as for casual, but competitive, constructed play is where an official ban list is going to matter.
If Card X renders a large amount of the card pool "filler", it is a problem. I realize making
every card equally competitive is a pipe dream, but
most should be for a passable game. Think of it like a homework assignment; if you're supposed to make well-balanced cards for competitive play, but less than 60% of the card pool comes out that way,
ya failed.