I don't think this is quite as good as Return to Karazhan but it is definitely the best dungeon in BFA.
I tried it with one group where we wiped 9 times on the first boss disbanding, the thing is the healer was really undergeared to the point where we barely survived charged smash.
the second group I was in was slightly better geared, around ilvl 405, this time it was much smoother, we one shot the first boss, then we wiped about 8 or 9 times on the slime boss before we got the mechanics nailed and boss killed, we oneshot the duo and in the process learned that killing Trixie before Neano makes Neano hit ridiculously hard. On the fourth boss we wiped once because as a tank I underestimated the damage of the Tankbuster add, we one shot the tussle tonks with relative ease although the Platinum Pummeler could do with a health reduction because after the other boss died it was a 3-4 minute slog with little to no difficulty. We wiped once on the dog because we accidently blew up a box before the massive aoe so we had nowhere to hide, Machinist was pretty straight forward just a ton of kiting and dodging stuff and finally King Mechagon, a oneshot and quite a let down I feel, the fight looks spectacular visually but I think it could do with being a little more challenging honestly.
All in all I think Blizzard have done a very good job with Operation: Mechagon.