Maybe it is just that I don't play very well. On a normal run on Floor 5, I encountered this room:
TunnelTall/Reath_TwistAndTurns.txt
Long story short, 5 seconds after I entered the room, all space was so covered with bullets that I could barely see the enemies. Fortunately for me, this time I had a full health seriously-damage-boosted Humble, to the point where I could insta kill most enemies with Contrishooter... And I ended up dashing through the tunnel of bullets and barely cleared the room without dying. The green cannon spreads numerous small dots across the room, and most enemies (that I barely have the attention to see) are what I call "area denial" type, in thin corridors.
Yeah, I don't know how to deal with these type of enemies in tiny space without overwhelming DPS on my side. Throughout this run, I could not find any good primary weapon (or secondaries. Or maybe I just ignored them because of the Contrashooter), so if I used another mech I would be doomed.
BTW, I am still not very used to the sudden health upgrade for enemies in Level 5. How much health is added for the enemies? They feel a lot tankier, somehow.
Sorry that I forgot to make a bug report save...