Because this mission kicked it.

Hard.

Feedback follows in three parts: Look, Play, and Suggestions.

Look

I LOVE the way everything looks in this new mission. Everything seems ooky and toxic, from the dying trees to the swirling pattern on the toxic-oiler-things. However, I don't love the way the entire screen fills with fire the same color as my enemies, making it impossible to see what I'm trying to shoot at, and making my party lag like miserable snail-creatures even on Low settings.

Play

Ow, ow, ow. For this entire mission, I was poisoned and on fire, most of the time with no good way of having avoided it. There's simply so much going on with such high durations that the whole thing felt like a race to see if I could kill all the (respawning!) enemies before I was chip-damaged to death... and even then, hearts, pills, and remedies were so scarce that I was sure to burn to death in the next room. I understand that the scorcher-oiler combo is what this mission leans on, but there's so MUCH of it that it feels unavoidable.

Suggestions

Legion of Almire is a very good kind of difficulty. The enemies are tough and the projectiles are numerous, but each time I would get hurt or die, it felt like it was MY fault that that happened, since their patterns were relatively predictable. I feel like, given time, I could learn to "beat" LoA; it would be tough, but with enough skill and practice, I could make every run a good one.

Not so with Compound 42. No matter what I try to do, I'm always on fire, because the enemies are on fire spewing more fire that turns into fire trails that fire fire fire. Oh, and I'm also poisoned, so any health capsules I have can't save me either. And shielding won't help because it catches on the oil spots, so all those poison-y-fire-y critters can catch up to me anyway. I don't feel, with the current state of things, like there's something I can DO to make up for it, as even resistant gear won't save you from being reafflicted ad infinitum. It makes for kind of a hopeless experience where I'm slowly dying without even being able to kill anything relevant. This is not a level I feel I could learn to beat.

On a more abstract note, I believe that most of the difficulty in Spiral Knights comes from restricting the player's ability to move. Traps, area effects, and projectiles all force players to move in specific ways that can push them into bad situations... if they aren't careful. Good players move profitably, bad players do not; even if they can avoid the hazards, maneuvering into corners with enemies will kill you just as fast. Difficulty contributes to fun, so this is a very good thing. FSC, Candlestick Keep, Arena third stages, and the Shadow Lairs are all excellent examples of this principle, and are rightly considered some of the most difficult and most fun sections of the game. Nowhere in any of those does it become IMPOSSIBLE to move profitably; in C42, however, it DOES become impossible to move profitably.

All that said, here are some suggestions in order of how badly I feel they're needed, with the spirit of the scorcher-oiler combo in mind. Some of them may be fixed by doing other things on the list:

1. Allow shields to block poison puddles without catching.
This is a damned-if-you-do, damned-if-you-don't situation. If I shield over it, I'm slowed to a crawl and an enemy will catch me. If I don't, I'm instantly poisoned and probably set on fire the next moment, since a Scorcher ignited it. Removing this would still leave the poison versus slow tension, but in a way that feels like an actual decision and not a choice of how you're going to die.

2. Reduce the duration of the poison, fire, or both.
In any other MMO, a constant slow drain effect (which is basically what this combo is) would be OK, because any other MMO has easy access to repeatable healing after it's worn off. Not so with Spiral Knights (a decision I love, but no less relevant). Slowing down the player's ability to damage which simultaneously chipping away at their life, with (once again) no good way to avoid it, feels much more purely frustrating than purely difficult. Fortunately, there are a number of ways one could go about this:
a) Give a flat reduction in the amount of poison and/or fire time that the player is afflicted with from the various sources.
b) Reduce the amount of time that oil spots or burning oil exists on the field. This would be my preference because it creates a changing network of safe/danger spots that players can actually respond to. Being able to avoid a hazard entirely both feels awesome and allows that hazard to still be strong to catch those that don't avoid it.
c) Add water balls so that we can at least put fire out.
d) Reduce the frequency of oil drops. This would probably be the least satisfying solution.

3. Add some hearts.
My party died slightly more frequently than every other room. Placing heart spawners or heart boxes at regular intervals would have significantly reduced this, as well as boosted morale. THis could easily be justified as a little first-aid station that the gremlins left behind. A full heal isn't even necessary; one heart box after every room would still make for quite the challenge, since you still need to survive the grind. This may not need to be fixed if the above changes are considered.

4. Slightly less SO MUCH FIRE.
It causes crazy lag and makes enemies impossible to see. A shadow fire-type graphic (with less opacity and fewer particles) would help, as would a graphic that was simply shorter so we could see the oilers moving over it. The gremlins, with darker colors, were much less difficult to see.

5. Slightly reduce the dash range for toxic oilers.
So many of them and so many stationary hazards to avoid means anywhere one tries to dodge comes within range of one of them... which makes them dash... which makes you poisoned. A slight range reduction would give players a bit more freedom to maneuver while still forcing them to keep their distance.

6. Remove the spike spin for toxic oilers.
Dealing with a deadly combo of status effects, quick enemies, and projectiles is already hectic enough; also trying to keep track of very fast, hard-to-see, status-inflicting projectiles that fire in random directions from the most common enemy just seems a little excessive. I will admit, however, that I'm not a huge fan of this attack on regular toxigels, so I may have a slight bias in suggesting this.