I like what you have so far
I love arena shooters, but I do have some suggestions that would make this game even better.
-wasd to move and mouse to aim/fire would be the ideal control scheme. As it is your guy turns too slowly and precision shooting is a pain. This is the most important thing to do right now.
-if you do change the controls, have icons for each special ability that you click on once to select, and then click again to activate
-have different weapons. Using the same one gets boring
-add obstacles to give you an advntage
-make the AI a little smarter if possible. like if the guys clustered together in a defensive circle instead of aimless wandering nd getting in my way
-faster base walking speed would be great
And yeah, those improvements would be a great start if you feel like improving this game. Please feel free to contact me if you need any more ideas or would like another review.