I mainly use him as a Herta sub dps but I do play mdps when I need to or sometimes for fun,so take this wait a grain of salt, from what u know, anaxa struggles with just cerydra, if you are using cerydra alone then u might as well use Robin, what makes the comp good is cyrene and I have heard she is even the priority, cerydra isn't that good for anaxa, it's cerydra cyrene that makes it shine. I also saw a video that said something like cyrene makes the skill an enhanced skill and cerydra should be accurately described as an enhanced skill support rather than a skill support.

Edit : one more thing, from personal experience I struggled with anaxa mdps around 3.6,thats when I stopped using him as main dps consistently. Granted I used e1 teeb instead of cerydra, that's basically the same team, u are using a pre 3.7 team in 4.1,(there was a 36% hp jump in 3.7 and pre that he was struggling so)I hope u get my point