In a way, it might seem weird, but Downton Abbey seems to have grasped something interesting about the 1st world war. I'm not saying they depicted it perfectly, but they seem to have understood pretty well how this war has sort of redefined the distinction between nobles and non-nobles.

They even say it, if I'm not mistaken, after the war, that "the war changed everything". Non-nobles participated in the war just as much (in fact, even more) than nobles, and this participation in the war did lead, in a way, to a redefinition of the gap between nobles and non nobles...

As for the violence of it all and the misconception, by the generals and other leaders, of the impacts of new technologies on the way the war is fought, I don't know of a lot of movies/series that depict it appropriately. It would be pretty difficult to do.

Here in Quebec, there was a series that has been produced about WW1. It's a documentary, and it's called Apocalypse. I think you can have english subtitles to it, but it's very very good. They extensively cover the subject of the war in 5 DVD's, and having followed classes in University on WW1 (when doing my bachelor's degree in history), I can tell you it's very accurate. You could try to look for this.