By goals for on per 60, Ales Hemsky has been above average until last year where there was certainly a problem.  But above average isn't "good".  By the scoring chances, his 2010 numbers were off by half compared to 2009, but the Oilers conversion rate with Hemsky on the ice remained low.  You can find the rest of the Oilers' power play chance numbers here.  Remember the caveat for the scoring chances - we're working with only two seasons of data and both of those seasons were abbreviated for Hemsky.  It's also worth noting Dustin Penner's numbers last season without  Hemsky for 60 games - his SCF/15 was 7.16 and his conversion rate was .208

Last note:  Opponents averaged 11.028 SCF/15 against Edmonton's putrid penalty kill this season.  Hemsky's SCF/15 2009-10 numbers were superior to the rest of the league against the league's worst penalty kill.

I've reached out to the other gentlemen who tracked scoring chances in 2010 to ask them to compile the power play scoring chance rates for their respective teams.  I tracked Florida's chances in 2010, but they were the worst power play in the league and using them as a comparison would make J.F. Jacques look good.