While it's realistic of course that other countries (and especially other continents) would speak another language, I think the only actual instance we see where another language is used is with Dragons who have their own words for certain things. The fact that not only the Player Character, but every other NPC in the game can speak with the Domans without any sort of language barrier either means that the Domans were exceptionally quick at picking up new languages, or everyone in the world just speaks Common, perhaps with various different dialects.
The only case where it is clearly stated that they speak another language, or are at least only able to be understood by people with the Echo are the Beast Tribes, but even that seems to have gone away completely in 2.0 as seen by the Beast Tribe dailies where regular people are capable of speaking with the Beastmen without the need for having the Echo.
The only case where it is clearly stated that they speak another language, or are at least only able to be understood by people with the Echo are the Beast Tribes, but even that seems to have gone away completely in 2.0 as seen by the Beast Tribe dailies where regular people are capable of speaking with the Beastmen without the need for having the Echo.