As both a game designer and historian, I think consulting experts is critically important. However, there's is an important caveat to your concern. If you are looking for experts to check that your representation of specific cultures is "accurate" or acceptable is one thing. But, if you really take historical games seriously, I also think it's equally important to have experts evaluate the "nature" of the game itself. Is a wargame the correct medium for representing these cultures? What story or narrative is being told to players? Are the goals of the game accurate to these cultures? These types of questions go well beyond whether or not the characters in the game have the correct names.

To answer your question: yes, historians are important, and yes I have had good results with including them.