Stats like xFIP aren't really designed to suggest how well the pitcher has pitched for a particular team, stadium, or league. They're designed to attempt to place all pitchers on a level playing field (by only taking into account data that the pitcher has somewhat direct control over) and evaluate how well each would have performed relative to each other if they faced the exact same batters, in the exact same parks and leagues, and with the same defense behind them.
We can't use xFIP to tell us what Dickey's numbers SHOULD look like this year pitching for us. To do so is a misapplication of the statistic. You would have to take something like xFIP as a base and scale it based on the ratios for the teams he's faced along with park factors and team defense factors or something.