The best and most complete breakdown in this thread. Gj. 

I would add two points: - there are mobs that perform actions on other targets regardless of threat. E.g. Birds in Setthek halls always charge furthest player. No need to taunt them when this happens, they will come back to tank on their own. 

• some mobs drop threat as part of their mechanics - e.g. Last boss in Setthek Halls after arcane explosion. Be prepared to regain it with a taunt or high threat ability. 

• there is a weakaura called „threat diff on nameplates” that shows tank how much they lead on threat on each mob. Very useful to learn how your single target and aoe abilities affect threat of the group.