That last sentence is a lot to do with match-up rather than anything else. Federer is a worse match up. Soderling can hit through Nadal on a good day and there's nothing the Spaniard could do about it, but Fed's variety can negate Soderling's strengths.
He never loses anywhere when healthy, the whole act is tedious and the main reason I'm not missing him on tour one bit.
It's not an act, it's well documented that he has had knee and foot problems for pretty much his whole career, and for you to say otherwise is just low.
IIRC he didn't look good in the Soderling match.