I just played here.
Id say that everything in general needs a lot more cover.
The cave one is boring, the pit has no cover at all, and the factory's spawns are to close together.
I would remove like one or two people from each round, and replace the spawns farther away from each other, that and add more cover like trees, stalactites, and more crates.
I have to disagree with this, the original arena game Lem and I made was meant to be hectic, it was four people in a 32 x 32 cage fighting for a special weapon at the center of the ring. To keep this alive we have brought the hecticness of the original arena back.
Some parts are a tiny bit bland, but other than that, it's great :D
You better come play, it's going to be fun. :P