Kirin would probably be the easiest of any major boss to do back then with an alliance of 65's, you'd just stack rangers and have a few spots for the entire alliance+ people had sitting on minis and swapping in to SW/CB. BLM's would land like 1/10 spells outside ES anyway. The fact that he's a kited mob means the tank level meant very litttle... they'd be in barney set instead of AF, and have some more hp, that's basically it back then. Nin boots came into play at 52, theoretically with whm sub and constant refreshes they could tank him at night at that level lol.
Also rangers were a big part of the kiting back then, striders > anything pld had without killing kirin in the first place.
Shadowbind rotations for the minis, 1 person kiting genbu, not a whole lot more to it.
Meanwhile plenty of groups full of 75's with the same amount of people have wiped to kirin plenty of times over the years.