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.
Maeve isn't actually strong aginst Maeve ,Inara has the slow deployable which slows in a short radius around her. This doesn't always work because it is stupid to verse a inara all by yourself when your maeve.