The only reason moving and attacking are useful is to kite one mob away from another. And just better positioning in boss battles while not hurting DPS. I used to PVP in World of Warcraft A LOT, and i've grown so used to moving around when attacking as a melee dps that I still do it in FFXIV, but it's not really needed at where I am in the game (level 27).

It'll become a much more valuable skill in PVP, even with a slower GCD.