Possibly a culture difference. On the JP servers, the de facto MT is ALWAYS the the B alliance tank for the entire run. All the other tanks defer to the B tank and control their aggro output to ensure it is not ripped off. Unless for some reason, they need to take it up eg. the MT dying etc or the B tank specifically requests in Alliance chat s/he is relinquishing the MT role. Never ran into a situation where tanks disagree or quarrel among themselves on who is MT or ST.

Saves alot of time and grief