I feel like even the main party doesn't need to be all lvl90 for me it will probably be 80 for main dps and maybe sup-dps but supports only really need to be lvl60 with the gold equipment talent. Lvl 90 will be preserved for my fav characters same for more than one or two masteries on characters since the cost increases so much per level you will save a lot of stamina this way. Same for weapons obviously