So for testing EDH decks I think your method works well.

But how I play test with my modern deck is I basically just decide what I’m playing against before I draw my 7. Either U/R Murktide, or Tron or whatever. Then I just play my deck normally but assume that the opponent has the best possible play every turn.

Murktide is T1 Ragavan, Nimble Pilferer, if it’s tron, they have natural tron turn 3 every time.

The “omenpaths” are just the plot device being used to set up whatever the next big bad is.

It could be some mysterious entity from a plane we don’t know about yet who gains access to a specific part of the multi verse.

Not a big chance that WOTC will blend the different identities together, because then the game loses its flavor.

The reason for different planes is for new mechanics and ideas to be introduced. If we were always on Dominaria, the difference between scrying and surveilling is more difficult to understand.

I liked the concept at first but the implementation of it was just meh. It honestly just feels like a bonus sheet that they forgot to put into the regular boosters.