No, I haven't read Quasar.
Neither the character or the writer or the artist appealed to me at all.
Wasn't Quasar in the Avengers for a while at one stage? Who wasn't?
I can't quite remember but I hated him wherever he turned up.
My opinion of Gruenwald is based solely on some Avengers he did after Simonson's equally undistinguished run and his Captain America. I thought both efforts were remarkably unremarkable.
The only project of Gruenwald's as a writer I ever enjoyed was when he finished up Roy Thomas' Celestials/Ragnarok epic in Thor. I think he wrote a few issues after that which IIRC were gosh aweful.
I do, however, believe he was involved as an editor in some projects that I do hold in high esteem like Born Again in Daredevil by Miller & Mazzuchelli.

As far as most of the other writers on the list, I would qualify them as competent writers of solid albeit predictable superhero fare. Nothing more, nothing less.
Claremont for instance, I consider an important writer because he wrote some absolutely classic material and he was probably the most influential mainstream comics writer since Stan Lee up until the early 80s. However, his influence was ultimately worse than it was beneficial and his classic period was relatively short. Basically, I think he was a spent creative force by the time Paul Smith left the X-Men with #175. After that he became a victim of his own successful, turning all his innovations into cliches. He basically became a poor parody of himself.

And then there's Kurt Busiek. Rather than finding his own voice, Busiek has made a career of finding other people's voices; Stan and Roy's in particular. He provides good, wholesome, reverential fanboy fare but it's hardly distinguished. Even his best work, Astro City, is highly derivative. He reminds me of a kid riding his bicycle without hands. It's pretty daring but it's still just a bike.

Englehart wrote some brilliant stuff but also a lot of extremely mediocre junk too. Even his highly-touted Avengers was sub-par up until the Celestial Madonna and it crashed pretty soon after that too. Of course, he was handicapped with some really crappy artists on the Avengers.