Make no mistake about it, Fitz benefits from having Boldin opposite him.
Sure it helps, but let's look at the games where Boldin didn't play at all:
2008: 5 Games, 28 rec., 528 yards, and 7 TD's
2007: 4 Games, 31 rec., 432 yards, and 2 TD's
2006: Boldin didn't miss a game
2005: 2 Games, 17 rec., 243 yards, and 1 TD
Fitz doesn't need Boldin to be great. Steve Breaston and Bryant Johnson were just fine.