Sayers & Mennie will go down as 2 of the unluckiest bowlers of the last few decades.
Sayers - 320 wickets, 26.5 avg, 2.6 economy, 59 strike rate
Mennie - 297 wickets, 26.1 avg, 2.8 economy, 55 strike rate
Very unlucky not to get more opportunities than a single test match each.
In fact, all of those guys you listed have phenomenal FC records, fast bowling depth certainly wasn't an issue over the last 5-10 years.
I just did SS.
Copeland for me was a genius. He will make a great bowling coach.