The Foundry beast fight seems legitimately unfair on dominating. Are gas grenades seriously the only way to kill the bladelings? Every other method seems to be a non-starter: shotguns are useless because the fuckers resist crit damage, plasma grenades don't do enough damage, and anything else will kill too few of them at a time. That's pretty irritating if you haven't invested enough in chemistry to craft gas grenades.
You need bear traps all over the spawn, the stairs, and down the right side hallway till the end of the fencing. Sometimes even a few more bear traps after that. If you have Gas grenades or Plasmas that are of a high enough level, use those first, but after that, switch to Frag Grenades. Caltrops are super huge too, specifically Crawler caltrops. Two of those and you'll make the fight so much easier. Do these things, and you'll be fine. I beat the Beast fight on Dominating with a Spear dude that was literally chucking grenades almost the entire time, minus the very end where he also did some tanking/body blocking.