[Ibrîniðilpathânezel]

Part of the issue here is the way in which LotR was written. In its structure, it's character-driven, not plot-driven. The essence of the story is not the war; it's the people who are involved in the war, how they are affected by it and how they in turn influence it. It's not about the politics and the larger socio-economic issues of war -- which of course are a part of it, but not the focus of it -- but of personal choices and actions. For that kind of story, it has more than enough action. The introduction of Théodred and the battle of Isen would have dragged in a short-lived character only for the purpose of showing action that, while politically and strategically important, was not so important that it needed to be shown, even in an extended flashback. I've heard plenty of people complain about the need to remember all the names of LotR's large "cast"; as he was presented, Théodred didn't add to that burden. What we needed to know was that a battle was fought that demoralized the Rohirrim and Théoden in particular. Did we need to see it happen? Not really. It would have slowed down the rest of the action.

Much the same can be said of the corsairs. As presented, the arrival of Aragorn in the ships is a welcome surprise rather than another battle that telegraphs the outcome of his choice to take the Paths of the Dead. When Gimli and Legolas tell the hobbits what happened, it comes close to slowing things down too greatly, but it's important information about the central characters, Aragorn in particular -- it's the first "return of the king," after a fashion, and important to the characters and the plot.

For my money, there was just the right amount of action a character centered plot. More action would have just been more action -- nice if you like it, but not really necessary, IMHO.