I'm not sure. I mean, where do we even draw that line? Dick was Robin after all; he's always had plenty in common with Bruce.
Far as I know, the Bat-lite stuff really started to become super obvious with the first solo. The Titans had become a dumpster fire and DC wanted to move Dick away from the property as much as they could. To his credit, Dixon did do a lot to establish that Nightwing was not just Batman Jr., despite a lot of similarities between them and Dick's return to street level adventures, but as less talented writers took over the book the Bat-lite parallels became more and more prevalent. I don't think I could point to any single issue and say "This is where it started." I think it's a slope; there's always been a lot of the Bat in Dick's makeup (again; he was Robin so of course there is) but it slowly took over as Dick's more unique traits became de-emphasized.
Like the Batgod, I don't think it's something that just happened, but was a slow evolution as writers looked at the work of better creators and took all the wrong lessons away from the work.
We did? Whatever. I'm surprised godlike is still reading that crap; I wouldn't pay good money for this. I wouldn't read it if it were free.