(Please note that the following is more from a reader’s perspective than from a writer’s. Also, I do not speak for all fantasy readers.)
Why do new fantasy authors feel the need to write archaic dialogue? I’ve noticed this time and time again where a rookie to the fantasy scene writes their characters’ dialogue in an old timey way (things like “I heard tell”, “For that is why…”, and so on). Have to say, not only is it cliche, but it makes it obvious to avid fantasy readers that you’re a total newb to the whole fantasy realm. Using dialogue like that takes away from the story because it looks like you’re trying too hard to follow the “fantasy formula”.
I’m not trying to tear down writers who start out like this. Heck, I did the whole archaic dialogue thing when I first started out, too (none of which will see the light of day) and that was when I was in the midst of reading The Wheel of Time. I’ve noticed quite often that the most engaging fantasy books use modern speech mechanics (even Sullivan did that much), so try to stay out of the trap of making your characters talk like they’re in a Shakespearian play.
If it helps, this is how I see it: you are telling a story that takes place on a completely different world in an entirely different language, so your job is to translate it into something modern day Earthlings will relate to and understand. For my own writing, I’ve found thinking that way has improved my dialogue greatly.
(This rather spontaneous post will probably make a lot more sense to you on Saturday.)