Lex has the loudest footsteps in the game. Turning off music and using good headphones might help you pinpoint his current position if he's behind a wall.
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!
Never jump back, because you risk to be killed very easily by champs like Androxus, Tyra and Viktor. Try instead on jumping very close to them so they get confused!
If you have Chain Reaction legendary, place some Sticky Bombs around Evie in Ice Block and time your detonation right, so you can punish her for staying in it for too long.