Yep, before I toned down the difficulty the game was virtually impossible to beat as the later waves send so many enemies at you that you're forced to mix in several rocket launchers or axes to even survive until the end. But looking at it after submitting the difficulty got toned down too much and it almost felt boring to play xD.
It's definitely really difficult to come up with a perfect balance, and it's something I'll definitely try to remember for future jams!