It isn’t optimal, no. But if you wanna use it nbd. You’ll lose physical damage reduction from no shield pretty sure, and of course your damage will fall.
But tbh, consider 3 DPS doing 180k damage each, a tank doing 120k, and you doing 40k. You as the healer then only contributed 6% of the damage. Not insignificant, but still. It’ll only make or break a key or raid encounter if you were right up against the timer or enrage.