The tank is not the default group leader. Many tanks are
the group leader, but it's not because they're the tank.
It's because they choose
to lead the group. The group leader can just as easily be a DPS or a healer.
99% of all planning and instructing happens out of combat. The requirements to successfully lead a group is knowledge of pulls and mechanics, the ability to explain said pulls and mechanics, and a way to make sure people are ready.
The only necessary equipment is a mouse, a keyboard, and a brain. Not tanking gear, not a tanking spec.
Leading a group has nothing
to do with tanking.
"Tanks are expected to know all the fight mechanics! That's why they lead!"
Anyone who has DPSed AND Tanked before can tell you that tanking is really just DPSing, except that your awareness of mob position is reversed. Everyone
should know all the mechanics. The only difference is which mechanics you need to pay attention to.
"Tanks have the most responsibility! That's why they lead!"
BS. Everyone is equally responsible in a flashpoint or OP, and nobody should be tunnel-visioned. Not even the DPS.
If the tank doesn't do his job, the boss gets lose and everybody dies.
If the healer doesn't do his job, the tank dies, the boss gets lose, and everybody dies.
If the dps doesn't do his job, the boss enrages, the tank dies, the boss gets lose, and everybody dies.
See a pattern here? The only reason the tank feels
special is because there are generally less tanks overall.
It's a job. Not a calling. Being tank only makes you as special as your spec and gear. It doesn't make you leader automatically.