Wow, need to check that game for tips. I normally still have a shell box from wiping Hell Arena, as with AoSh an Int2 arena is sort of a cakewalk unless you get swarmed in an instant at the start of the next wave. But a combat shotgun is not a frequent drop on Phobos lv5, and even if I do get that AND a P-mod to augment it at once, I seem to get cornered by barons pretty often. I have managed to get some of them with relative safety, but then that moment happens when a baron enters left doors with you engaged in damaging one (or two!) other barons, you have to flee as in cramped quarters that baron has an advantage, and you normally can't push it back out of the doors and maybe into the lava... OW, OW, AAAAAHHHHHH! And since there's no cover outside, you're pretty much screwed. Then yet again, the Vile. I couldn't down it last time on UV with zerk on at first and a double shotty plus Shottyman AND HR2 (no combat shotgun for me that time), got it to mortally wounded before it fried me.
I start to clear Deimos Lab and NOT releasing the shamblers, they are too dam tough and mobile to tackle, perhaps if I'd be a zerker then maaaybe I'd decode to communicate to them my need of packs (:D), but likely not on any other setting. The location where they appear is too small for ranged combat and too hot for melee, should they start teleporting (which I think they never do if engaged, still one needs to close the distance first). One Shambler is doable, esp if you can take some cover after it teleports. Just did a successful AoSh run tho, gonna post a mortem as it has something to boast on my skill level.