Whenever you're up against a Maeve, your Fireball will be necessary as Maeve is more than able to kill you from a distance. If you're alone with a Maeve and not at low health, you can put up your shield and retreat, or burn her with the fireballs.
Sha Lin is the ultimate way of telling you to get out of the sky - and when you're on the ground, Impaler Arrow is a huge threat for you. Resilience will be necessary; a good Sha Lin will deal too much damage for Haven to be effective.
Ash's ultimate ability, Assert Dominance doesn't give her CC immunity at all or Damage immunity until she lands. You can use Void Grip to keep Ash in the air after her leap and let your team kill her before the ult lands.