'Providing a DS is hard'
Well actually it's not (and don't forget I did it for 34 years when it was called RAS and before it was called DS) provided the controller provides 'quality' traffic information as well as vectoring aircraft clear of conflictions. The easiest ones were the fastest; with a Buccaneer doing 500kts at 2000ft (legal 'cos he's military) you could look 10 miles ahead, point it at a gap in traffic and know he would be OK.
More recently with the advent of TCAS which I disliked intensely, I used it to advantage passing traffic info to an aircraft under DS (or RAS as it was then) and my aircraft replying 'we've got it on TCAS, no confliction' and there it was on the tape so if there was an Airprox report, I was covered as was the pilot.
I can't comment on your MOR of last week because I don't know the exact circumstances.(maybe Sonic does)