i never saw any servers for them iirc
I actually used to host Boss Fights with them. For those who have played along with in the past, everyone can more or less remember Solaris and Frostbite.
I typically like the bosses due to the sheer ingenuity. These characters were nothing like your Dragons or Bugs.
My best guess is that if you actually finish the mod, more people might be interested at this stage. Sure, it looks good, with a couple of characters already half-done, but people like tend to like finished products.
As for myself, I just like to beta test stuff. And so far, I've beta tested that mod so much in my "boss battles" that I found a few interesting bugs. So, yeah.