Thanks for the feedback <3 I hope you still had fun besides the issues.
The level spawns are still not great, I wanted the game to be feature-complete before getting to carefully design them. However that's besides the point.
I think I need to provide a counter-measure to the stone throwing enemies. That could be adding a 360 upgrade to the rangers or a way to be able to manipulate their position. Have you tried using Magnus or Spearman by the way? I think especially Magnus is still quite over-powered and could get those guys easily. Not sure from what you wrote but another possibility is that the stone throwing guys might have been pushed out of the arena by other enemies (that is a known bug).