I know you want dedicated figures for Gondor and Rohan and I would definitely agree on Gondor, however, I don't think you could do much better than Lucky Toys Huns for Easterlings, much criticised as being too fantastical for real Huns but great for fantasy.

Thanks for backing me on Gondor! But Rohan does need specific figs as well! Yje Huns might be good for human allied to Sauron, but Rohirum? Not a chance!

Rohirrim are mounted Vikings, so i think Rus could work well.
Of course a set or more of properly Riders of the Mark are a real luxury.

While i see Easterlings more like Samurai...