Q didn't have the kind of onscreen chemistry with Sisko that he had with Picard or Janeway. All Sisko wanted to do was punch Q in the face...otherwise Sisko wanted nothing to do with him. At least Picard and Janeway sort of enjoyed sparring with Q. Sisko would have none of it.
As for Barclay, I totally identified with that guy. Barclay was much more realistic than any other character we've seen, IMHO. At least Barclay had faults. He wasn't the ultra-perfect type that Gene was always trying to put out there.
Q was a character that was meant as a foil for Picard's stuffiness and self righteous smugness. He was a being that was so powerful, that even Picard with his underlying self righteousness, was forced to bow once in a while to Q. Janeway fits that profile also, because she was basically female Picard, even down to the Rambo antics.
Sisko on the other hand was a very angry character, and he's damn lucky Q found his over the top uncontrolled anger amusing, otherwise he could have just turned him into a terallian amoeba permanently.