Fear causes attacking units to run to exit tiles & leave combat. This makes the effect lopsided.. It can effectively remove units from battle which makes it objectively more powerful than similar potency effects; but only when applied to an attacking force.
This becomes extremely frustrating in the case of Mass Battlefield Panic which can be used as the ultimate siege-denial ability for any army that is not completely immune to the effect.
Army w/out total fear immunity attacks -> defender gets first action -> casts mass battlefield panic -> 1/3 (or more) of the attacking army leaves combat, loses all movement in the strategic turn, and the siege is essentially delayed infinitely until the defender doesn’t have casting points or the attacker manages to field units with strong will across the board.
I understand that fleeing from combat makes sense from a lore perspective of the panic effect(s) but its a terribly imbalanced tactical implementation. Even when used against a defender (that can’t flee from combat) fear effects are still very powerful and do not need the additional result-shifting effect of removing units completely.
At the very least Panic/Fear effects need not cause attacking units to leave the tactical grid. I would further suggest the alteration of the Panicked unit to “run” on the tactical grid for one turn, and stand still “cowering in fear” on the second turn of the effect. The change would make Panic/Fear effects slightly more consistent in their net-effect; sometimes better/worse for the force affected; but probably the best part – overall, is that it would tend to shorten tactical combat length without majorly shifting outcome by negating the necessity of resolving the full use of a feared units travel away (and often) back to battle.