Having written the setting I'd say that languages are basically just something that hasn't been adressed that much yet. We could have done it, sure, but we could have done a lot of things and perhaps we'll some day do them. It's more been a priority thing.
That said, I would assume that there is a pretty much widespread ”Common tongue”, probaby affected by dwarven, elven and human languages. This is what you speak when you try to communicate with those of other background. It's understood basically everywhere. The common tongue might however not be a proper language as we percieve it, but more of a pidgin language, a mix, with a base of perhaps 50% recognizable ”common” words and 50% local words joined together by a simplified and fleeting grammar. So when you listen to a stranger, you listen for the parts you recognize and try to patch the rest together into coherent information. People in Ravenland thus wouldn't expect a language, but look for communication with whatever means they have in common – hence ”common language”. If we were to have linguistics as a talent, perhaps that would be flexibility in expression and the ability to understand a lot of variation, rather than ”learning”, since there isn't anything to learn.
Concerning humans, alderlanders and ailanders came from overseas. The aslenes didn't, but the spoken human tongue in Ravenland is probably a mix of the two groups of languages. During the isolation, lots of local dialects and words arose.
Elven language might not necessarily have the ”Tolkienesque” notion of being noble and staying the same over time. The Ravenland elves might actually distrust language as such, since it never amounts to more than a simple approximation of reality, leading your thoughts and perceptions away from what actually is to the ready-made pictures in your head. I wouldn't be surprised if they distrust language and use it only as an evil necessity. They might aim more at mindfulness and perceptivity. Also they might aim for a personalized style in expression. Perhaps they tire of too-well known words and replace these when they get too watered down? ”Today I will call a 'horse' a 'door' for a change!”
Dwarves probably have the most stable language, a very practical tongue based in their ancient religious beliefs and crafts.