mimartin

Concussive shot is helpful for Shepard because of Adrenaline Rush (the evolution that allows him to use one power while AR is active) and by extension, for power combos.

Normally, for combat combos, the trigger action has to kill the target in order to fulfill the combo, however this is not the case for enemies stunned by disruptor ammo (all you have to do is hit them while stunned). Since this is what Ash has, she doesn't need to have a lot of points in CS to use combos. Also, now that disruptor ammo is effective against barriers, she doesn't need it to fight Banshees.

Same thing goes for Garrus with Overload/CS.