While I really disliked the idea of going around killing people just because they want to talk to you (!?), I'll try and focus on what I found is the main problem, gameplay-wise.
I found that the best strategy was to never stop shooting and kill the enemies while they were out of view (or at least damage them good enough that you can kill them very fast once they appear). This leads to very poor gameplay. To solve it I would do one of two things:
- Reduce rate of fire, zoom back the camera and allow the player to see more ahead of him.
- Reduce range of the gun but make it way more powerful (think shotgun).
Keep making games!