LotR Wiki which admittedly is fan made, the armies of Rohan were all mounted, while their infantry was more a well-trained militia called upon in time of war. What heroes will they name? Theoden? Eomer? Eowyn? Maybe Hama, Gamling, Grimbold, and Erkenbrand, but they were definitely secondary characters. You might get Eorl the Young and Helm Hammerhand just as readily. Playing a predominantly infantry Rohan army led by two second string characters isn't a theme, it's simply playing for rules advantage. It's the equivalent of flier spam in 40k. While technically it could happen (Necrons surely have a lot of aircraft) you don't pick it for the theme, but because it's the stronger list.
Now I'll grant that I've become more of a theme player over the years, I play bike marines generally just because I like bikes. I'll continue to work on my mounted Rohan army (with Theoden and Eomer) because I like the imagery that attaches itself to them. I might even paint up some warriors of Rohan on foot to fight alongside them (along with the three hunters). I accept that themed lists are sometimes more difficult to play with. However I do wonder why playing the predominant theme of Rohan is actively discouraged by the way the rules work.
Still, with the changes to throwing weapons, and the ability of all Riders to carry a bow now, I'm confident my éored will be interesting to play.