The daily rate of change is plotted below:
During the storm period 3 days show increased loss. Over the 2007 loss this is 292812 sq km
WUWT claim that this loss exposed more ice to later attack but only 2 other periods show gross changes:
During the period 15th August to 17th August (additional loss over 2007 is 178438 sq km)
During the period 22nd August to 23rd August (additional loss over 2007 is 174687 sq km)
So the Absolute maximum loss that could possibly be attributed to the "Great Arctic Storm" of 2012 is 645937 sq km.
The difference between the 2007 and 2012 minimum is 765468sq km
So even if you subtract the largest possible storm induced loss you would still have a 119531 sq km additional loss in 2012 when compared to 2007.