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.
If Meave isn't using Artful Dodger, and you have Surprise Attack, break hidden with Poison Bolts and do your hit her once from behind. Follow that up by using smoke screen to hide yourself and let the damage encourage Maeve to retreat.
If you see Evie uses Ice Block and stays in it to heal, Charge your shot and aim for the head. there is a small window where Evie can't take action after Ice Block and you can one shot her as she comes out.
If you can see and kill Ying, Prioritize her over her Illusions. Killing Ying makes her Illusions despawn and prevents her from Healing/Shattering. If you can't see Ying and have no/low cauterize killing Illusions might stop healing from her.