Giving healers 100% accuracy in Cleric Stance would leave the DPS and tanks rather perplexed as to why the stat even exists any more. You can't give a healer a free stat cap to facilitate damage that the other jobs don't get when it isn't even their role.

Damage from healers is a bonus. If you want to maximize your damage output then by all means sacrifice your healing output to meld accuracy on your gear. If SE gave healers accuracy on Cleric Stance expect to see the damage bonus from Cleric Stance removed to compensate.