SpellBlade skill clarification (DM)

Looking at the adverseries, in particular the Spellblade under Mercenaries, they have an ability called Suppressing Blast
mark a stress and target a group within far range. they must make an agility reaction roll or take 2D12 magic damage. Add a token to the action tracker for each target that marked HP on this attack

What is confusing me is they have a range but not a radius, it just says “Group” to me that would be all PC in the far range distance. This makes the ability feel very overpowered for only a single stress.

Has anyone used this before or have suggestions or clarification on this ability.