Does making the writer agent and the reviewer a separate instance actually beat one-agent self-critique?

A question for people running multi-agent setups for real. I've been building a doc-to-wiki system, and early on I made the writing agent and the reviewing agent separate instances — the one that drafts a page never reviews it. The reasoning was that when a single agent grades its own output it tends to wave it through, and separating them did seem to cut that: nothing ships unless a deterministic lint pass and a separate qualitative review both agree. But I keep wondering if I'm over-engineering. How much of that would I get just by prompting one agent to self-critique in a second pass — same context, no separate instance? The split costs real orchestration (five roles in my case: reporter, columnist, desk, copy editor, editor-in-chief), and I'm not sure where the line is. Related thing I'm testing: when the same review failure recurs, the system drafts a change to its own authoring guidelines and keeps it only if a blind before/after on a fixed regression set shows it helped (Self-Harness / SkillOpt style). Still measuring whether that's signal or noise. For those who've shipped multi-agent: where does the writer/reviewer split actually pay for itself, and where is a single agent with a critique step good enough?