WAR is a stat that separates (or attempts to based on ones viewpoint) you from your teammates. It puts (or again, tries to put) every player in the league on an even playing field so they can be compared.
You claim he is more valuable than 1.7 wins because the depth of the Reds pitching stinks, right? That would inflate the "worth" of all the Reds starters then in your eyes, no? I get that if Arroyo disappeared last year the Reds probably would have lost a few more games. But that is different than his WAR.