Cofagrigus is definitely C Rank in my opinion. I have used it a bit, and it does have potential. It's a neat bulky Ghost for offensive teams, and its OTR set is pretty cool as a sweeper; it's one of the more viable TR users around and after an NP boost its power is pretty sufficient, and the fact that Steel doesn't resist Ghost anymore is also a cool thing in Cofagrigus's favor. Will-O-Wisp is a fun move too to cripple physical attackers, especially Tyranitar, while making better use of its awesome bulk. Its bulk and NP are what set it apart from Gengar and Aegislash as an offensive Ghost imo, and Mummy is also a cool ability to remove the abilities of Pokemon like Talonflame and Azumarill. It does have flaws like its lack of recovery, two common weaknesses, and competition from other Ghosts, but it has a decent enough niche to warrant a mention here.
Ninetales though I see as more of a D Rank Pokemon if you ask me. Yes, sun is a pretty good playstyle, especially with some new ones like Megazard Y and to an extent Mega Houndoom, but beyond that Ninetales is still really mediocre. It has trouble staying alive due to its terrible vulnerability to hazards, and it's also very weak. Yes, hazards are easier to remove now thanks to Defog, but that still doesn't change the fact that Ninetales sucks. The new limitations to Drought really hinder its usefulness, as well as the prominence of Megazard Y. That's probably me though.
Donphan should be D Rank (or C Rank at highest) imo because it's outclassed by other spinners, and its lack of recovery and inability to wall that many threats in OU which make it struggle as a spinner. It's not that great at spinning because it has a lot of trouble staying alive. It does have a decent enough of a niche to warrant mentioning here.
Jolteon, Milotic, Machamp, Mienshao, Avalugg, Shuckle, Zoroark, Meowstic, Bronzong, Azelf, Rotom-Mow, Virizion, Yanmega, and Sharpedo are all irrelevant/unviable in OU and don't deserve to be on the list at all.
I'll refrain from commenting on the rest of those proposals though.