First off I say if there is no BLM there to sleep and you are the only sleep at low level dungeons sleep the adds, just do it, take control of your pt you are the healer you are not theirs to command you are there to keep them alive. Frankly if you are low level and are sleeping it means you have no BLM, if you have no BLM at those lower lvls you really lack the AOE firepower to DPS as a group effectively early on you also lack the healing potency and abilities to effectively cover your pt. Your party, your responsibility, your tank, your healing rules you don't want to risk it, DON'T. In the end remember who they will be crying about if their body hits the floor regardless of what you do or do not do. I had a tank once that did NOT want regen on him at any point regardless, ok well that's his call, his job and his responsibility so I rolled with it. Chin up you got this, do whatever you feel is right to keep your pt alive, that is your torch to bear.