No. The only thing they were important for was knowing that there were border conflicts causing bloodshed, but these border conflicts were all linked to events involving the Amestris military, so it didn't matter. The plot was entirely Amestris focussed, though with some backstory originating in Xerxes and Ishval, which were both sufficiently touched upon (though not if you only watched brotherhood, I guess, in the case of Ishval)
And Xing was only important because of the background/motivations it provided for the Xingese characters.
Also, we saw 5 Xingese: Han, Fu, Lan Fan, May, and, of course, Ling <3. 6 if you count Xiao Mei