Just went through the ODST Campaign for the 3rd time going for this specific achievement. On Legendary with a party of 4 and not using any playlist or skulls. If you included the streets levels we still made it under 3 hours. No achievement. All my times are recorded on my stats page here for every level and total under 3 hours. Any updates on achievement bugs 343i?. Thanks!
Update: It just randomly unlocked while I was on another game today. Which is odd since it was not “Done / Unlocking…” either.
So I guess this topic can be locked/closed.