I'm used to the somewhat more normal "accumulative" threat in other MMOs, where if there aren't any "1 shot" mechanics, the tank can generally AFK after the first minute or so.
EnMasse's TERA seems to work very differently. On my priest, I find myself pulling aggro constantly, even late in the fight. From a Lancer's perspective as well, it seems like they need to stay exposed most of the time (and take a good deal damage) or hit the AoE taunt on CD.
It's fairly obvious that this threat mechanism isn't accumulative, but are there any hard rules for how it works?