I agree, that while it wasn't a steady run through those years that set the world on fire, there were some good issues in that 1977-1982 period.
Some nice art by Jim Sherman, and Mike Nasser. With some great inkers like Bob McLeod and Bob Wiacek. There was one issue, number 262, with Jim Sherman pencils and inks, and it was really nice, but completely differnt from the issues he just pencilled.
Three good issues by Jim Starlin in 239 and 250-251, and a few nice covers too. One issue ( 238) where Starlin did a nice wraparound cover, with a 2-issue reprint of a Shooter, Swan/Klein ADVENTURE COMICS story, even as a reprint it was beautiful.

Jim Janes did some good art, and as far as I know, the only series he worked on, around issues 268-281.

And as you say, a number of really nice Perez covers in the year or so prior to Giffen starting on the series.

It looked to me like they were setting up Broderick to be the regular series artist. And then pushed Broderick aside, to have Giffen do the series. And while I love Broderick, I think Giffen was the perfect artist at that time. There was tremendous energy in that 284-306 run, it was a sight to behold when those issues were coming out every month. The Levitz/Giffen run was both a huge leap forward in quality, and also consistent with and a wonderful tribute to the 25 years of continuity that preceded it.