My whole group did the 40/40 and the longest one was 50ish minutes.
Blood Gate with Unholy DK / DH combo, everyone was geared (448+) and could press buttons (r.io 1.7k+). Looting and bagspace was the only issue, because nobody was AFKing and mobs spawned instantly all the time.
I did not claim I did it in sub 1 hour with LFR heroes watching asmongolds stream, but it was just a regular PUG with filtered randoms.