I would actually say that the rebellion would've happened a LOT faster if not for the Graft, and things probably would've happened as you say. I highly doubt it would've taken 45 years to come to fruition. The similarity created between humans and Cardassians is an example, to my mind, of Dominion arrogance backfiring. Not only did they not think that either species would find it in themselves to rebel, they actually DID NOT imagine that the two would collaborate as they did. (And that coordination, I suspect, was
partly humanity. They were altered, yes, but I think the human talent we saw on Trek of opening up to other species and forming ties--go back to ENT for the ultimate example--was there. I SUSPECT that the humans made the first overtures of friendship, as time passed, and that opened the way later for the Cardassians to speak of rebellion as those relationships grew close enough and trusting enough to allow it. I think that while humans got the Graft, some of the openness, the lessening of arrogance towards other species, may have been an influence in the other direction.)
The Dominion did what they did because they were frightened of what humanity might do if left unchecked. They thought they could achieve some sort of balance between innate obedience and free will to where they could get the technology and the creative thinking that they wanted but not have to fear a rebellion. They mistakenly thought that the Cardassians--the source of the Graft material--lacked the ability to rebel, and that therefore so would humans if they were changed. They screwed up with regards to the Cardassians (we know from the prime universe that they WERE capable of rebellion once someone lit the flame), and their mistake carried over to humanity as well.
The trouble is, I think you may not be taking into account the difficulties that came about because of what the Dominion did. Even if you look at JUST what the hero of the story went through, or, say, imagine what the doctor went through when he realized what was happening and that he wasn't allowed to fight it, or any number of people...even if it doesn't show in some sort of display of chaos, you're going to have a society that is VERY severely affected by what's happened on deeper, more personal levels. Humanity's collective self-confidence took a heavy blow. Making sense of yourself, making sense of your family, neighbors, and co-workers--all of that was to some degree affected.
The role the Cardassians played, as I see it, was more...snapping the altered humans out of their fears and helping with their inexperience in understanding themselves as they had become. They were not leading the humans around necessarily, unless it was providing an example that yes, this CAN be done. I saw the gul as more saying, "Don't underestimate what you're capable of...there IS a way if you're committed!" Once they got started, it was a collaborative effort and that's why I'm not specific on who discovered what, technologically. (We DO know, however, that the idea of delaying the bomb explosions by so long came from the narrator, an altered human who very much remembers his past.) The gul was leading, perhaps, but I think it may have been a simple matter of who had the most command experience in that particular group, as well as a matter of self-confidence. It's not a speciesist thing. Humans may have led other cells; I have to think the rebellion, to pull off something as widespread as they did, HAD to have been somewhat decentralized. I don't know for sure, though...it depends on what individuals were where and who had access to what resources.