Personally, I don't see much of a reason to make a distinction between "best WR" and "best overall WR". Sure, the latter includes things like run blocking, but I don't know how important that really is. I don't have any data to support this, but I suspect a WRs run blocking ability is analogous to a pitcher's defense. Is it an asset? Absolutely. But it's such a small part of their job, that I would generally only use it for tiebreakers. Essentially, as great of a blocker as Hines Ward is, I don't feel that skill is important enough to vault him ahead of the Larry Fitzgeralds of the world.
With that said, I would put Larry Fitzgerald at the top of the best WR class.