Question about tanking an aoes in endgame trash

[MahoSenshi]

From a MNK perspective (since they have the most positionals):

If >= 3 mobs, DPS should be doing their AoE rotation, so move as you like... (BUT!!!) try to clump mobs closer together as possible. Many melee AoEs have line or really small circle zone, and too often tanks don't bother themselves with clumping.
Example:

M...M
...T...
M.....

This is bad, Rockbreaker on any of the mobs will not hit another two. Same for Howling Fist, Geirskogul etc.

If 2 or 1 mobs then sure, try not to do excess moving. Escaping from AoE is fine, especially if you move back right after red cone/circle fade. Less damage to the tank - more time for a healer (well, for a good healer at least) to DPS, so total group damage is bigger.