Do you think the different species in the show should have distinct accents? Yaks do but everyone else sounds the same. I would think that they would be able to identify each species based on how they talk, even if we as the audience can't tell.
I like that idea. It would have been cool if the dragons had a specific accent, apart from Spike since he grew up with ponies. It would also show how he's from a different place without having it described to people.