So I have the explorer perk and none of the locations are visible on the Pip-boy map unless I discover them

That's by design.

I think this ones popped up with every DLC release.

The explorer perk is only going to work for content installed when the perk is taken. And I've never tried, but is it even going to effect DLC content anyway?

well i should atleast see the undscovered map location...maybe the designers should have anticipated new DLC map locations. I mean, this isnt the first DLC to come out. I understand coding takes a stupid amount of time and effort but we couldnt have added a preservation to the trigger for the explorer perk?

If I am to read Jason's implication correctly. You wouldn't get the lonesome road locations even if you took the perk afterwards.