Khan is usually only a threat to the backline when he has his ultimate. Stay behind or inside your Frontline's shield to prolong or avoid Khan's ultimate completely as he cannot grab anyone behind a Shield.
If you happen to come across Khan, use the environment to your advantage. Get hits from a distance, run around, and get more hits on him. His relatively small shield lets you get more shots at him, too.
While Maeve is best at flying around an open map, a closed environment doesn't hinder her performance. Use Prowl to speed around corners, and jump INTO corners to confuse the enemy.