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.
Learn how to bunnyhop and you can hop out when sniping the enemy Sha Lin across the map. It would confuse him seeing you flying up in the air and lunging across the map a pretty far distance. Learn how here: https://youtu.be/2rYToy5eUas?t=315
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.
If Pip is pressured, you might force him to use his Healing Potion on himself to survive or if he's playing selfishly. Cauterize helps alot in countering him.