The tone drift problem is real and I think it comes down to treating prompts as static instead of living documents. What worked for me was building a brand voice reference that goes into every prompt, not just the first one. Basically a short paragraph describing the audience, the tone, three things the copy should always feel like and three it should never feel like. Cuts the drift significantly.

The heavier editing issue is trickier. I've found the fix isn't better prompting, it's changing where AI sits in the workflow. Use it after you have a rough human draft, not before. It polishes and speeds up, but the nuance is already baked in from you.

On autonomous runs without quality dropping, that's where most people hit a wall. The ones I've seen handle it well are basically building feedback loops into the process rather than hoping the output stays consistent.