Lex is a flank champion, yes but he has a very restricted movement, and he can't move vertically, so he's easy to spot and easy to predict where he's coming from.
so get to a high ground, mine the entrance, and you should always have the upper hand.
A good tip is if you run Faustian Bargain, you can technically bait Furia into trying to kill you, then let it run out, use it again, behind her, and hit your abilities on her, and it would be a free kill.
Makoa It's really effective in short distances, so try to be far away from him and throw it Sticky Bombs in the distance. With the Demolition Talent, you can destroy the shield of Makoa really easily with the Grumpy Bomb.