That would make it have numerous uses. Maybe not in Darkrai/Hydreigon, but in Garchomp and other stage 2 decks with multiple Evolution lines it could be quite helpful. It could also be helpful in other decks that only need 1 of the Evolution line they are getting. When you put 2 of the basics of that Evolution line down in case one gets KOed, if one doesn't get KOed you just have a basic there with nothing to do with it. If you put down 2 Dittos instead, you could evolve one into the Stage1/2 you needed, and evolve the other into something else you needed, or even just a basic.
Ditto can also be used for a surprise factor. Your opponent could have no idea what the stage 2 in your deck might be, or you could even use it to transform into a fully charged basic or EX, instead of needing to charge up the basic or EX on your bench which would put it at risk of Catcher.
Ditto can also be used for a surprise factor. Your opponent could have no idea what the stage 2 in your deck might be, or you could even use it to transform into a fully charged basic or EX, instead of needing to charge up the basic or EX on your bench which would put it at risk of Catcher.