Ash's shield is small compared to the other tank character's shields (Height-Wise). If you can, try to get above her shield or go around it to attack her.
Right before Andro's Reversal shuts off you can send your fully charged shot at him (easy to headshot him when he's trying to position for Reversal) and hit him before the green things are gone. Pay attention to the sound of his Reversal.
When Drogoz is airborne, try snapping almost directly in an upward direction then snapping to his location horizontally. I do this when playing and seem to easily headshot him mid-air on a regular basis. example: https://youtu.be/DGVWJDimNv4?t=83