Well, my first Legendary party was: Lem, Harsk, Lini, Ezren, Meri, Amiri. It worked well, although Into the Mountains was a pain. Of all of the characters not in this group, I think I miss Seelah the most. I'd be inclined to maybe swap out Amiri for her, although Amiri's movement abilities are certainly nice on Legendary with a 6-person party.
My second Legendary party was suggested somewhere on this forum, and was actually great fun to play: Lem, Seelah, Kyra and Lini. All of the divine casters. It worked really well, although Kyra is rather superfluous.
I have also completed the content available thus far on Legendary with solo Lem, and solo Sajan. Both were a bit tricky to get going, but ultimately the went pretty smoothly. I actually feel that Lem might be one of the most well-suited characters for solo play, in spite of the pre-role uselessness of his bardic talent. His ability to switch out cards at the start of the turn is fantastic.