It's so annoying that every tank thinks they are the 'leader'. Just because you have a sword and target the mobs first does not give you license to act like a spoiled princess. Yes, tanking sucks and it has a lot of responsibility-which is why tanks are rarer and hard to get from DF, but that does not mean your job is any more important than the DPS or the healer. I swear, sometimes I DF with tanks who act like BRDs/RDMs did in FFXI: "I'm special and irreplaceable and if you don't do what I say, I'm leaving because you all waited 40min for me, but I can insta-queue at any time"

Tanks protect the party.
Healers sustain the party.
DPS progress the party.