Pure healing is mostly useless. If in an Oddy or a Reagent, have double attack pattern beta so you're boosting your teammates dps. If not, at least have one; that way you're at least carrying your weight in the dps race even if its technically not you doing the damage.
In the top end of play even the escorts can tank and heal themselves, so really, try to maximize your damage output, then slot in necessary heals; extend shields, haz emitters and aux to structural are the major ones you should have if you want to be a support ship.
Science boats, don't waste your shield damage potential in favour of being a healer. Simply put, there's no reason why you can't do both.