Ok so I have some questions about tanking that are subjective to opinion but welcomed regardless.

1. When should I switch from tank stance to dps stance?
2. When pulling large mobs, is there any particular order I should target or just randomly switch between enemies?
3. On boss fights, what cool downs order should I have? Is there a penalty to having more than one gcd up at a time?
4. Why do people pull for tanks if healer can t keep up?(This doesn't happen on every dungeon but I always ask healer if they are ok with big pulls or small, yet someone starts pulling anyways when the healer specifically said small...frustrating)