I am playing with Dunland now. They are, of course, meant to be a minor evil faction (in fact, so minor, that Isengard got access to their troops on their own settlements), and, theoretically, the weakest one, being human, but being borderline caveman level. Well, they may be primitive, but I can't really say they are weak. I am going around with a big Crebain/Raven Rider host (as usual, cavalry army for strategic mobility), and they do pack a wallop with their plentiful javelins, being useful even in sieges. Take a bit of micro in the battlefield, but surprisingly, not much, as they don't seem to use the javelins as last resource, unlike Rhovanion Marchwardens (and not being from a secondary troop line also helps with fielding numbers). Not sure about their other troops, as I only saw their stats, but in general, Dunlanding's very low level and stout troop tree means you can get the "elites" quicker, which is very handy, allowing you to have a semi-orc gameplay style, but without ravenous troops and having the kill a lieutenant every two days.
That said, maybe they could be a bit expanded to get out of the shadow of Isengard? Maybe have their troop tree upgraded/changed after taking Rohan down, using looted equipment and/or attracting other tribes from Enedwaith to the war. Also the chieftain sword bonus of reducing their upkeep is really unnecessary, considering how cheap the troops are.
Edit: I also would like to point out that despite their equipment being very primitive, it is not nearly as bad as it seems. The antler ax hits pretty hard with a decent reach, while the war axe hits very hard with a much smaller reach. Javelins also hit very hard, and their highest tier of armor is competent, being roughly equivalent to Khand medium armor despite looking like an amalgam of rust and stinky hides.
Edit 2: After one of my lords died, we pretty much stopped all campaigns. We are not sieging anymore, just patrolling. I think I will disable lord deaths next game.