I think the cover makes it pretty clear who one of those characters is.As for the series in general, I think most of the characters are quite interesting. I haven't really had any issues with the large cast, and actually quite welcome the fresh perspective provided by characters like Huilan and Chaka. I hope the series continues like this through Destiny and beyond.
I can promise that in Over a Torrent Sea, you'll get fresh insights into the perspectives of a number of alien crewmembers, including several who haven't previously been explored in depth. (And "in depth" is an appropriate choice of words here, in two cases in particular.)
http://startrek.wikia.com/wiki/Image:Over_a_Torrent_Sea.jpg
