Insight You've Gained by Playing Different Jobs

[Lemuria]

Tanks need to stand still, so melees can hit mobs/do positionals.

Not entirely sure I agree with this one, but for one sole reason. Getting hit by strong AoE isn't generally wise in any circumstance. A smart tank will be able to move out of the attack range and slide back into position while their attack animation plays out, both avoiding the damage AND keeping the mob relatively stable. At least, that's what I do.

This way you both minimize the damage, which is a tanks primary job, and make things far less bothersome for positional attacks from your melee.

[kyuven]

This way you both minimize the damage, which is a tanks primary job, and make things far less bothersome for positional attacks from your melee.

This is part of why tank is one of my top 3 classes. While lower level runs can be like watching paint dry (during ifrit and Titan SM, I don't even technically have to MOVE while tanking) all the other instances have you moving more than most other classes...but it's not the OH GOD DODGE DODGE DODGE WHEW movement where you can cross the map. You have to move in subtle ways and then move BACK as soon as possible.
Honestly if you manage to get any of the tanking relics, you're pretty set for having some intuition as to when and how to dodge. I recommend doing so for anyone interested in raiding. It's not even that hard since tank queues are so short AND they usually get the in need bonus.