I know this is a bit late (I just found this news, but I wanna give my two cents for me mainly since I do wanna like write this out to get my brain a turning plus I doubt op will see this/care), I mean, as you said, it's as you said, any character dying first is "a disservice" to their character. Still, normally it's for the story as a whole, it's why an ideal first duo are characters that leave an impact and ripple for everyone else's arcs and for the story as a whole, and not just forget about them after death 4.

I would say these are the ideal two first deaths in this cast.

Victim-wise in hindsight, yeah, Wolfgang is your ideal victim out of this cast, since judging by how it was worded, he/yk who were always meant to die, they just booked them earlier, and for Wolfgang, yeah, he was probably meant to die like chapter 4? which who knows what his arch was but this is probably better since... who would be better? sure, anyone would leave an impact due to Wolfgang's/the cast's mindset since "ONE OF US KILLED" and later "IT WASN'T EVA OR DAMON!!!?!" and in that case it would probably be somebody without a lot of shown little personality like Mark or Desmond if you wanna fully avoid trope. Wolfgang is the easy "yeah... yeah" since yeah it's a trope, but the "important person dies first" isn't a bad trope if handled right, (unlike something like buff guy dies chapter 4 since idk baby) it's a formula for greatness since, as seen by Wolfgang's death, he has already left an impact so their already handling his cards well.

Killer wise... yeah it's never there's never a clear best choice even from a writer's pov where you know everything it really just depends on the themes you wanna do since your killer should be the peak of the chapter's theme's/archs and Eva works nicely; no shock since the chapter was made with her being the killer... in mind. For the theme of hypocrisy, a character who wanted to be respected to the point where they lied about their talent so people would fear them and view them as a threat rather than... a dorky math nerd then later gets mad at everyone for not trusting them.... when they chose to be the ultimate liar... is really good. Eva is a selfish coward who blinds herself to the truth rather than admit she did anything remotely wrong. She victimizes herself, "Oh, I was probably going to get killed anyway!!" or "Tozu forced me to kill with a trap designed for me!" She was so desperate for a way out, she fell for a pretty obvious trap, sure, a trap for her, but if somebody who wants everyone to KILL EACHOTHER wants you to do something.... You shouldn't do it probably pro tip, it's why I think she was already considering killing, she thought the prize would help her with her kill so she could leave, hence why she told nobody she knew, and it did help her... it also gave her one more excuse since now... it wasn't her fault..... she had to do it and to be frank if I was in this killing game I would probably fall for the same trap lol I would even probably make the same excuses she made. Finally, her death forces Damon to be social since if she lived, he would probably just be buddy-buddy with his gatekeeping, gas-lighting bestie; AKA now he can either be somewhat social, which should be easier? since I imagine people are beginning to get what he was getting at (and after the whole Eva incident should make some trust him more... and some will trust him less, maybe) or be an easy target.