I wouldn't say they are less relevant that the last 1-2 drafts because we don't even know if players from the last 1-2 drafts are busts yet. But too each their own. Does data count from earlier times? I don't see why not and I don't see a reason to cut off at one specific year or another. Unless you think something has drastically changed in overseas development, I don't know why those years would not be relevant.
Not enough for me to say that overseas players are worse than American prospects, but kudos for actually coming to the table with something. I genuinely respect the effort. I'm just not personally not convinced that overseas prospects are better or worse than their American counterpoints. If I like or dislike a player. it's not going to be on the basis of them being international or not.
Just for the conversations sake I will go back 20 years total.