if we use it so can they. normally we are also outnumbered, at times significantly. could be this is a way to keep your melee characters from dying so quickly to sudden bumrush of enemies.
just food for thought, and discussion.
I would have no issues with this, though.
Right now I don't really find myself needing to put a ton of thought into positioning. A lot of stuff can be brute-forced, though at least with Flanking Advantage being a thing, your casters would have more of a reason to cast a wider variety of spells.
On Shadowheart for example, I don't cast anything but her Healing spells a lot of the time, but this could put more use into other spells like Shield of Faith, etc.