The logic of the former Does Not Follow, and the latter is my position.
It's simple.
1) The Tank Stance toggle lets the Tank focus on pushing their buttons, attacking, healing (if applicable), mitigating, keeping things pointed, and still having an engaging amount of junk they can do. They are still generating good threat and not locked to the old 1-2-3 combo that made tanking a boring drone in order to be doing your job well. They can adapt to the situation without being on the edge of their seat about if they can keep aggro on that fourth mob that the BLM has a Blast Romance going on with.
2) Tanks want and need some way to manage their enmity generation in order to hold threat or not, if they are in a situation where there is more than one person in the Tank role. Otherwise it is very hard to prevent "fighting for aggro" when they do not intend to. Not everyone has the same skill, the same gear, ping and rotation speeds, so there's plenty of fiddly bits that would make aggro start bouncing around just from those normal mismatches. The simple way to do this is to let them have a toggle that turns the multiplier on or off.
"But wait!" you say. "There's Provoke!" A Tank that is geared, seasoned, and determined will take that piddly lead and snap it like a twig, especially if the Tank using Provoke isn't any of those. But when you have multiple Tanks with varying skill levels, it's just a recipe for Aggro Pinball.
