Q only got ONE episode on DS9??? Preposterous! He didn't have to come back as frequently as he was on TNG, but come on!!!
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.
My favorite Barclay line in Trek history (from 'The Nth Degree'):
(on being told by the computer that there is no 'neural scan interface' in the records)
Barclay: No problem...here's how you BUILD it!
I just love how totally exasperated Reg sounds, like it's the most obvious thing in the world.