1.5 seconds is exagerated. 2.5, maybe 2 with slide casting, remember RDM pack no spellspeed.

But yeh half of the time you can move, during your combo you can move (granted around the boss) and worst case you have 1 to 2 reprise per cycle if I remember correctly.

You can anticipate some mechanics and move little by little to the spot before.

Of course it's not as good / safe as aetherial manipulation on BLM or the insta casts on SMN, but it is not a turret either.