I see bot party with 3 chars (1 spoiler titan and rogue) and they xp with out buffer . Who they do that??? After 85 lvl we lose mentor buffs where we can bot ???

After 85 you do loose mentor buffs, so if they are pre 85 they will be using mentor buffs, if they 85+ maybe they have brought buffs from an ISS in town, buff potions, or have an ISS out of party somewhere?

Maybe use npc buff until -90, 1 hour duration.