Those are strong words my man.
My group is currently holding 6 minute buffs on P7S which is why I go RDM on this fight over SMN. Doing an analysis, I noticed SMN is still really stronk and way over RDM unlike p8s second boss.
https://xivanalysis.com/fflogs/2yhJV...pe=damage-done Clear with a group that don't hold buffs with a SMN in it. 9m22s clear time.
https://www.fflogs.com/reports/Zn8LT...pe=damage-done Clear with a BLM they do hold buffs and clear at 9m16s.
Summary; the entire group lose 1-2 GCD by not holding their buffs for the Summoner. That's the only reason they'd lose on those buffs because it cost them more to have the one summoner desync on the last buff window. You were saying Summoner is the easiest to optimize? Having an entire party adjust for Summoner doesn't sounds
easy