Try to separate him from his turrets and wait out his shield because of the short duration of the shield. Do not let him be first on point and set up turrets.
Your shadow travel can make you immune to everything. Use it to cancel ultimates and abilities, or use it in sticky situations. (I recommend using veil since it can make you go into shadow travel faster.)
Slither cancels Hunter's Mark. Giving your position as a healer is bad, so it may be a good idea to slither away to get rid of it. You can still heal your teammates from a distance!
When sniping an Evie who is about to leave Ice Block, aim a little bit in front of her path in the direction she's facing because she will usually blink after leaving the block and tends to walk forward a bit first.