It's tempting to get deft hands when you know you'll have difficulty with flanks, but you should get your reload speed from your loadout instead. This will allow you to get cauterize so you can keep down the enemy frontline and help your tank further
Create a loadout that has snake pit II or III in it (probably less if you have two tanks to heal) and practice nailing your stuns. If you stay grouped and land a stun, evie will get deleted. Try to stun her right as she comes out of ice block.
Just remember that Lex has to be close to you in order to maximize his damage output, so poke from long - mid in order to have the best chance against him, because your daggers don't have a damage fall off (´・ω・`)