I was investing pts on agility mastery on my evie and when I went to rank A, it shows maxed but also below it, it shows "Nxt Rank 9 AP Req 960"
??? What is going on?

that isnt a glitch thats the same thing that happens for standing endurance

http://vindictusdb.com/skill?i=Agility+Mastery

so i cant go over rank A?

It's probably just maxed for you level or current progression in the game. Mine does the same for battle respiration, but I noticed it said I need to be level 45 to rank it up.

im lvl 66.. lvl req is only 45 so def bugged.

Must be, sorry I'm still a low level. :/

Max for those should be A until a later patch date.