tuxgeo
Adventurer
I think the "outlander" is like the "person from a foreign culture in the pseudo-medieval melieu." So it might cover folks like stereotypical nordic-barbarian-culture folks, people like pseudo-Arabic nomads from the desert, or even possibly "Merchant from Kara-Tur." . . .
I think outlander means "doesn't live in civilization, but not necessarily shuns people.” Tribal, nomadic, bandits, wardens, or people living on the edges of civilization (but still in contact with it) would be outlanders.
Any and/or all of the above! I think it means "not from around here," which covers an immense amount of territory.
Planars? Check. Barbarians? Check. Sorcerers of an unknown power source? Check. Miracle-workers who worship a pantheon nobody "around here" has ever heard of? Check.
It's too broad, in one sense: what skills would be possessed by everybody who is "not from around here?" But it's too narrow, in another sense: what single feature would convey enough foreign-ness to cover such a wide variety of different types?
One way, which I don't think WotC will have decided to use, would be this:
• Every PC with the "Outlander" background gets Perception -- because everyone willl want to take it anyway.
• Roll 1d12 on the Table for your second skill proficiency. Guides get Survival, but Horse-Traders get Animal Handling, and so on.
That might work. (But, again, I doubt they did it that way.)