A super solid concept here - the most I want from this is some UI feedback. A health bar in addition to the numbers, and maybe some more visual confirmation when picking up XP or the timer would go miles.
The first few play-throughs I was playing aggressively and not evasively, for some reason I had it in my head I had to just go for kills. Maybe screen flashes and visual feedback will deter new players from this. Excited to see more!