I know people don't like bringing Final Fantasy XI into this but you know in terms of end game content XI probably was one of the rare mmo's that did it right (to an extent) where they failed was the claim system so most of the hnm's etc on 72hr+ windows were claimed by which shell had the best bot, but looking past that.

Dynamis - Can be entered with up to 18 players (full alliance in XI - 3 parties of 6) it is an alternate dimension of the home towns where you fight plenty of mobs to get currency(relic related in XI) and AF2 gear.

Sky - Big open area where every mob is a danger - got to beat NM's in the area to get pop items to summon one of the 4 sky gods (Genbu, Byakko, Seiryu and Suzaku) When you defeat all 4 get a pop item to summon Kirin.

Sea - Pretty much Sky but whole new area new 4 bosses and when killing the 4th boss there is a chance absolute virtue would spawn.

Limbus - was designed to be like Dynamis but CoP themed(the expansion for Sea)

ZNM's - This was a new pop system which was excellent - you buy a 1st tier item kill a boss and it drops an item for the next tier to spawn another boss each tier getting harder till eventually you can spawn pandemonium warden which at the 75 cap was extremely hard to beat.

Now imagine all this content dropping the same ilvl gear - pretty much what XI did for years and years and it worked since gear was unique stat wise - like in every game some gear was trash and some gear was good hell for some situations going back for some 71-74 gear could be considered BIS since it can contain stats such as damage reduction. I think for BLM/RDM the staffs in the 50-60 range was BIS since there was a hidden ability giving more damage with the particular element staff.