This is pretty fun! The visuals are excellent, everything was very responsive. Gameplay wise this is very solid. Sound was also very good, and the little sayings that the heroes would do were funny.
As for potential improvements, [now that you aren't under the wire!], it would be good to have some sort of click-to-continue after getting a verbal warning; that took me by surprise several times. In a similar vein, it would be great if the second ability gave some sort of warning that it was getting ready to run out, like if it started to blink or something.
Two things that would be nice but not at the same level of the first two - spawning with no enemies on screen would prevent the need to click like a madman the moment you spawned. The other is kind of an 'overdrive' mode; if you keep progressing without dying / getting promoted, it's actually getting much much harder more quickly as you don't have a new ability to help with the stronger enemies. Of course you have the benefit of getting closer to the next promotion and reducing your risk for the next round when you overkill, but it would be cool to also enter some sort of bonus EXP mode or something to compensate.
Also - there's a bug where you lose the ability to quick-attack / click. It happens whenever I click out of the game (so, basically when I'm trying to hit an enemy on the edge). It usually comes back after several seconds, but I've had a couple where it stayed bugged for 7+ seconds, aka more than long enough for me to get hammered!