Livan has put together a pretty nice first half. The team has won 11 of his 18 starts, so I don't know how he is a "bum". The Nationals have scored a total of 64 runs in those 18 starts (3.55/start they average 4.25/start for the rest of the starters) while he has allowed 45 in his 117+ innings.
What stands out is he has only allowed 1 unearned run on a team that has allowed 47, but that could be because the Nats average 2/3 as many errors when Livan is on the mound.
In a league that averages 4.39 runs per game, anytime your offense scores 5 or more runs you should win, if they score 3 or less, you should lose. The Nats have lost one game Livan started where they scored at least 5 runs (June 26 @ Baltimore) but have won 4 games where they scored 3 or fewer. Yeah Livan can throw some clunkers, but he manages to luck into those games when the offense decides to take the same game off.