Is the mean 100 on a year-by-year basis, since this is not adjusted by eras?
It's not only adjusted by league average each year, but by park factor.
I also think WAR is perhaps the worst idea in the history of sports analysis. It just leads to lazy and wrong-headed analysis. The kind of analysis of simply regurgitating received wisdom without thinking about it that the early sabermetricians hated so much.
Oh, and Hunter had a great year that he had about zero chance of duplicating. I do think people are ignoring the great year Hunter had, so its not like Hamilton adds a lot of production relative to last season, but he's still clearly an upgrade.