I was under the impression that the dialects should vary greatly from clan to clan, or else Surinen and Narayad would not have spoken so freely infront of Rog. Does that work for everyone? Or have I presented a problem? Maybe they would have a similar root, but have become disimilar as the years have passed, so that there are some shared words but sentence patterns and many words or pronuncations sound strange or unrecognizable. If the clans have chosen to remain somewhat isolated I can see this happening.
Also, for all involved in the Eagle clan's activities, Latah is not a traitor to the clan. Just wanted to make that announcement publicly. She's a good girl, she is, and we have plans for her.
EDIT: I just saw your post Pio, and agree with it. Those who have some need to communicate with the clans might learn some dialects, and also some clansman might also know common speach, but not all because they would not generally need to know it.