He is 2nd in fielding independent ERA (FIP) with 2.54. Scherzer leads with 1.93. Kershaw's ERA+ is a good, but unspectacular, 120 (10th place is 135). The last two years it was 194 and 201.
(One thing from Fangraphs: Kershaw trails only Scherzer in FIP-, which is FIP ERA adjusted for park effects. Click here to see the rankings.)
The bad luck might be his relatively high average allowed with runners in scoring position. The table below shows his stats this year with RISP, no runners on and with runners on. The table after that shows his career stats.
As you can see, he normally does not get hit relatively hard with RISP. Usually, his average with RISP is less than with none on. But this year it is .064 higher.
Now he has only had 79 ABs with RISP. But if his RISP AVG were .214 instead of .278, it would be 5 fewer hits. If that meant 5 fewer runs, his ERA falls to 2.68. If it were, say, 7 runs, it would be 2.53.
On the other hand, his SLG allowed with none on is a bit higher than with runners on this year while for his career it is the opposite. If he allowed a .342 SLG with runners on, it would only add 1.085 total bases (over 155 ABs). That's like one more double. Probably a much smaller effect on ERA than the AVG with RISP issue.