as a dps raider, when i run df dungeons and meet some non-raider tanks, i would easily rip aggro from them, on almost everything, sometimes even dungeon bosses
but I do know my limit, as a Drg, i have more defense and hp than any other jobs except the 3 tanks, so if i was on opener, and i rip aggro half way, then i wud just pop either bloodbath or keen flurry to ease the pain for healer, and after my opener, if what i was hitting still alive, then i will consider shud i elusive jump, depends on if the thing was dying fast enough that i dont reli need to waste time on that one particular target, neither should the tank, he should by then acknowledge that he probably should spend more time and attention on other mobs. i have always tell my fellow tanks from FC or static, when we try to do dungeon runs, to not to worry abt the one that i rip aggro of them, just focus on others would be fine, by the time u fight that aggro with me it's dead anyways, then u eventually are gonna easily end up losing aggro on other mobs, and those cud be way worse, cuz they would run to the healer very probably
if i rip aggro of the boss, i usually give the tank several sec to put his own pants on, if he still failing the get it bak, then i will elusive jump
so all i wanna say is, overtaunt or not, detaunt or not, they are situational.
it would need the tank and dps themselves to make judgement at that very moment, those were never always straight calls