Instead of WAR, I think it's more valuable to look at the + stats (OBPS+, AVG+, SLG+) etc. That gives you the best idea of how a guy did against the rest of the league.
I DO like the concept of defensive WAR because it at least attempts to put a value on a player's defensive ability. The average fan cannot do this. I mean, everyone raves about Miguel Cabrera as the best player in the world right now. He is definitely the best offensive player currently, but (overall) Trout is better when you take into account his defensive ability. Unless you crunch those numbers, you don't fully understand that fact.