Chang wasn't feared by the best if they were in decent form and no he certainly wasn't capable of beating anyone at their best, he was a lesser version of Hewitt who wouldn't sniff #1 if he was the same generation as Fed (Roger doesn't go on walkabout when CC season arrives), the guy's vastly overrated in comparison to players like Roddick and Hewitt (courtesy of being a player in Sampras era instead of Fed's, I'm sure he'd be called another weak era clown if he were Fed's punching bag instead of Pete's).
Goran was a dangerous opponent and a terrific grasscourter at his best but was also a huge headcase who could implode at any given moment.
Winning % and number of titles matter little when it comes to slam performances, as I said for me it was the same as Fed's win over Sampras at Wimbledon, a solid win but nothing special.
I understand your thinking. I may disagree a bit with Chang but overall I agree.