He's still very slow, spdef weak, and has to be choice locked to actually get those kos. I remember when the tier had Mega Mawile, a similarly strong pokemon that actually had priority and an ability to switch move.

Is he an upper tier threat? Sure. His stats are pretty dumb so he's never going to be less that great, but a lot of the tier actually naturally checks him. Ferro, Corv, Rotom-H, Toad etc. do well. He can be a bit too strong in balance vs HO though, since nothing in HO takes a hit from him. His staying in the tier would solidify the move towards fat teams that has been going on since the Home release. If I had to vote I'd vote for a ban honestly, but not beacuse Melmetal's broken, but because it makes the tier boring af.