Dear DPS.

[Allyrion]

Dear Tank,

Stop moving randomly after you get the mob/aggro.

-DRG

Tanks that do the shuffle are the worst. No, I guess the ones that circle the mob constantly are, but they're less common.
There was a few tanks I came across that had to stand so close to the mob that their models were merged.
This caused the mobs to always be twitching and repositioning. Though they probably wouldn't if they could just take their fingers off the movement keys.