You know that for that clear to happen the fight had to go through a whole expansion worth of powercreep right? Powercreep so hard that right now that fight has been cleared with only 6 people.
Meanwhile we had a
no healer clear of TOP on the same patch it was released without need of any kind of powercreep. We also had
solo healer clear of DSR on the same pacth it was released.
That's the big difference, for those no dps, solo tanks, etc, to happen the fight had to go through powercreep to the point its current difficulty is not representative of what its original intended design was, meanwhile with healers we are seeing those kind of clears without any kind of powercreep involved, those fights are at their historical peak of difficulty and still don't demand the tools that only 2 healers can bring.