The way I see it, you'll want to be fistweaving either when there is low raid / tank damage going on that can be covered by other healers and your eminence healing or perhaps when the boss has a damage modifier e.g. Elegon. Standing still doing nothing is definitely not wanted, especially during progress when you need all the damage you can get. Of course, if you need to save mana for incoming damage then don't spend it on jab, fistweaving is a bit harsh on mana. But that's up to the player to decide if he can afford to do some melee DPS.
Also, being in melee range will be beneficial to you for on demand chi from jab, if you need those chi like on the moment for uplift or EnvM. Technically, jab is the least expensive chi builder in terms of mana, however it doesn't mean it's the most efficient. Healing through soothing mists should be more beneficial because of the healing it provides and the constant chi generation.