You should put a mine at your current position or at a point where you know he MUST come around. As you hear your mine you have 2 choices: 1.you kill him 2.you use your teleport to get away I would recommend to teleport to/near your team.
If RMB, you Reversal. Reversal will reduce Lex to low HP. You should always pick the Dark Stalker card. A good way to counter him Is to just out-damage him. You survive more shots than he.
When Evie leaves Ice Block, there's a brief moment where she vulnerable before she can Blink away. Time your Pounce and Daggers to finish Evie off if her HP is low, or for some parting damage if she has the Reprive legendary card.