Btw, which site is considered the best for WAR comparisons? It feels very made up in this instance. Certainly it's a great comparative stat, but how can baseball-reference and fangraphs be this completely different?
Also, I wouldn't say the NL is THAT much easier to pitch in than the AL. Maybe you allow more home runs due to more pitchers parks, but it's not like if Dickey or Kershaw were in the AL they'd give up 30 more runs a season. There's a reason the last two World Series have been won by the NL. (Yes, Dempster got lit up by the Yankees and the Angels, but he was NOT going to maintain that low ERA, in the NL or the AL. Remember he gave up 3+ runs in his two starts leaving the NL to the Pirates and the Cardinals.)