In order to get evade, you have to get attacked. Firing a weapon does not get you evade skill gains. One way to get your evader profession up is to let yourself get swarmed by exars and use a fap 50 or something. This way you get all skills from the evader profession plus fapping skills.
If you're killing the mobs before the get to you, you're not going to get evade. Of course in that case, you probably won't need it either.
