10/10 atmosphere and creepiness, really solid game and overall I just really hope you keep adding more to this.
Edit, also game spoilers: I guess if I were to point at the thing I liked the least it'd be Heavy's behaviour.
The other two completely fit the atmosphere while still somewhat behaving like tf2 classes. Heavy... doesn't follow this rule at all and is mostly an annoyance, plus his entire model isn't on screen unlike the other two. Kind of disappointing for the face of the game.
Since you don't have any classes that attack your front, how about Heavy doing this? Slow when far away but at closer distances runs you down after a moment of "spinning up". Shooting could just stun him instead, long enough to break sightlines and set him back to his slow mode.