"While 'Mass' buff is active on the Priest, it increases the range of all Treatment spells by (Mass Rank LV)."
Increase the base range of Treatment spells from 1 to 4 range, and double it when using Staff-type weapons.
Currently, it's almost impossible to make an efficient use of this, without losing all of your momentum to chase after allies and sometimes Priests having to use Rescue in order to treat people can become quite annoying for who's being treated, as you're in the fray of combat, and then out of nowhere you're hooked away, just to waste momentum as the enemy runs away or something.
I know if Mass does Treatment in an AoE, so that's out of my considerations. Hell no. We already got Lantern Bearer.