Look at this way: King theoden costs 5 points more than a standard king of men, has identical stats but theoden has 2 less will and 1 more fate, imo a normal king of men is better, the reason why not having will is so important is that its very likely you will come up against wraiths and theoden is such an easy target because he has no power to resist. One way to combat this is to use the legolas' autohit rule on the wraith(s) then boost your rolls with might, but even so its very risky to have a hero with no will
Regarding Eomer: you have Eowyn, who already has 2 might points, so she can call the heroic moves for you and is like 40 points cheaper than eomer and she still gets 4 dice to wound if she charges on horseback and wins the fight. There is a new version of eomer with 3 attacks/wounds on the GW site that is pretty neat but he's still a risky choice due to the fact glorfindel costs the same as mounted super eomer...
Im a big fan of theoden, he's one of my favorite characters, and it annoys me that he is so poorly portrayed in the game: By that i mean having no will points just because saruman casted a spell on him, which is not a reflection of his character, he was a very brave and willful man that rode to the aid of gondor even though gondor did not send any help to helms deep. I combat this logic by using halbarads statline (minus the bow) and using the option for the banner, as a purchasable special rule rather than a piece of equipment.
If you find many characters that you like having displeasing statlines, there is a user on the site called whafrog who has made an excellent website devoted to making more correct profiles for certain characters