I really like the tunnels, they introduce an interesting dynamic feature. Also, good job on the new, "little" friends, looking forward to seeing them in the full release.
I'll test the Spiderants now, I hope to reach Round 20 for a complete impression.
Edit: Problem. I got into a round with the Shotgun Challenge and Body Shot modifiers. On normal enemies without a Shotgun, crits would heal enemies, apparently the crit modifier became negative. On Spiderant Badasses even Shotgun crits would heal them, only melee dealt normal crit damage. DOTs and body shots were the only way to deal damage to them but they have huge resistances to both.
I used Moxxi gear for this, didn't think about using other stuff. Sorry about that.
Aside from that, the crit modifiers for BA Spiderants were quite reasonable. And here is some lol: