Magmortar,while very powerful,isn't fast enough even in such a low tier to be any thing like Chomp,it does need to go UU though.Magmortar is seeming more and more like Garchomp...
To be honest, that was either a mistake in the spreadsheet or I accidentally removed it when copying the list. I have gone through all the numbers again to double check everything and that is the only mistake that seems to have arisen. Sorry about that.
Edit: It was definitely deleted by me from the list on accident before I posted it because I added it to UU on the site but forgot to remove it from NU.
Magmortar has always had 2 major weaknesses: It's predictability and it's lacking speed. MANY threats in the tier outspeed and OHKO it and a number can come in on a resisted hit and force it out again. Broken rain will be broken though.. sigh..