Biolapse
Honestly, probably one of the worse maps that have been made in recent times. From my experience, maps like Evacuation Point, Blackwood Asylum, Monster Ball and Sanitarium are generally better since most firefights often devolve into S+M1 while hoping that a few stray bullets are headshots. With almost no option for escape in the possible rooms, getting outmaneuvered seems like an eventuality and Level 25 ZED Time skills won't save you. Unless you plan on playing six-man games consisting of 3 Zerkers and 3 Medics, you probably won't be getting very far.
Also, the objectives seem to be tied with RNG AGAIN because it's a "The Descent"-style map where you enter new rooms each wave, and two of the random rooms need to be selected for you to get the relevant hazard kills. While less egregious than Yuletide Horrors' Matriarch objective, you'll still find yourself farming those kills more than you'll enjoy the content for what it offers. In fact, I think the only map that really succeeded in implementing usable hazards was Monster Ball, since the hazards and relevant buttons were more or less along the way to your escape routes thus allowing the player to thin otherwise overwhelming crowds with the environment.
HRG Incendiary Rifle
Definitely a welcome addition to the Firebug arsenal, though it does make the MAC-10 pointless. Also, the name is kind of bland. Rather than nerfing the HRG rifle to be in line with the MAC-10, here's what I think could be done
HRG Incendiary Rifle
Give it a more unique name. Like, "HRG Firedrake" or "HRG Balrog". Heck, I think a 12-year old just joining some random Korean free-to-play MMO can come up with a cooler name than the generic-sounding "HRG Incendiary Rifle"
MAC-10
DoT tick damage increased to 18 (was 8.5)
Base damage increased to 28 (was 25)
Rate of fire decreased to 760 (was 895)
Bullets have a 20% chance to explode into ground fires
Thinking a rate of fire decrease and a slight damage boost would be an overall buff as that can allow the player to better control their shooting. The insane RoF and low damage seems like you'll be wasting half your shots.
Overall
I dunno what to make of this update cuz it feels like Tripwire's current monetization model has underperformed, cuz it's definitely a lot more underwhelming than the Grim Treatments and Yuletide Horrors updates. If we are to absolutely have less content later down the line, i wonder if it'd be better to stick with paid characters rather than paid weapons.