@Devastator
You know, I don't buy it into "didn't kill anyone". Hasn't he basically dismembered pretty much everyone down below (maybe apart from one or two people, I don't remember the details)? You know, people die if they are killed, or specifically dismembered in this case. It might take it a little time to have them bleed to death on the heap of their own entrails, but death's a death, even if it hasn't yet set in, or is temporarily reversible one. Think Charro Hootzal.
The problem is, what I think you'd desire to see, more common perma-deaths. And here it breaks up: a 'permanent' death is a meta-game term, that has no place in-game. We're not zombies for enemies to target our heads as the only way to stop us - killing us, even just dismembering us a little bit does the trick just as well. And while "recoverable brains for later revival" is a thing from IC perspective, I don't see any enemy going after those except for maybe someone specifically bent on denying us brains and slightly psychopatic at that - maybe the serial killer would fit, I don't know.
All the AoP had to do was to take us out of action. Even if he wanted to kill us all here and now (and not, say, protect the cargo from our intrusion, hypothetically), just leaving us up to the liquefying device would work. Only ampers in brain-cases could still pose a threat when dismembered, and adjusting for no inputs would still make it difficult for them - I think Lyra was either overlooked, or left for later.
So - no, he did optimally and almost wiped the team. 'Almost' here being the result of Steve's intervention, which he apparently wasn't prepared for, and not the Arbiter's incompetence or inefficiency (by design or by Piecewise going soft on us). And Steve's intervention wasn't Deux Ex Machina (in the sense of completely unexpected help coming out of the blue), it was a carefully planned and developed project that was mentioned or at least hinted at for quite some time now (thus rather classifying it as Chekhov's Gun, if you wish).