Lex deals too much damage to fight on your own. If you're under attack from him, use Shadow Travel and move to a safer location, then regroup with your team.

Try to wait until Fernando's shield is down before ulting, as it will block the line of sight of the ult.

Treacherous Ground shuts down Maeve's mobility quite handily if you can catch her with it, but be wary of nearby terrain. A smart Maeve can use some bits of map geometry to get above the effect of Warder's Field and become free from the cripple.

Yagorath is a massive unprotected hitbox, ripe for the Blastflower talent. Your damage will easily ramp up against her, and she will be forced to retreat or die.