Detachment is not the absence of emotion, it is the process of becoming one with the Oneness that is the Universe. To be detached, is to realize that the fullness of all there is, is too much to react to with just one emotion, one thought, or any bias. To be detached, is to acknowledge all, without owning any of it. To be detached, is to summon forth the whole entirety of understanding, to the fragment that is the void.
True healers know that wellness is the order of the day, so they do not allow themselves, even for a moment, to see anything other than that. So, the power of the healer is in the power to influence the one who needs to be healed into a vibration that allows the healing that they are summoning. (that they could get, even without the healer, but they can get faster with a healer's influence).