WAR gets talked about all the time and D-WAR might be the worse yet. AJ for example, 3.4 last year for D-WAR, better than anyone else in both leagues. Blew Trout's 2012 away. This year its .8. No way AJ got that much worse. If you don't get the opportunities to make great plays in big situations they can't be made and D-WAR doesn't have a chance to improve.
Its a worthless stat.
Not entirely worthless, but yeah, it's pretty bad.
UZR, over the sample of one season, is basically worthless.
But over multiple years it actually has some value, though still far from being perfect, just helps give you a general range of how good a defender is.