Well, that's what I said, only the Cyrads and a few Narsi did it.
And as Tim pointed out in that same post:
And is it a possible way to go to other planes,as the ethereal touches all other planes ?
The Arali have never tried it....
They have had groups who were Mistwalking in the past get lost in the mists and never return.
So, it might be possible but it does seem to be a one-way trip as you are probably lacking the right conditions over yonder and thus can't come back, if you survive the new place.
Maybe a Gazetteer on Mist Walking would be a good idea ... maybe one about the different means of transportation on Cyradon, i.e. Mist Walking, Portals and the like.
Also, as Mist Walking is not as strenuous as travelling through a portal, I guess an elven contingent could with the right herbs and spells very well travel through the "Mist" for a couple of days to move from one continent to the other, BUT that's my interpretation and my version of Cyradon.