Yeah, it is a messy mess. Has pretty much unviable things like Sylveon (which should get the ax IMO, seeing as it's now UU.) Tyrantrum (just use Tyranitar), Mega Ampharos, and Mega Houndoom (both of which are horrible wastes of your Mega slots, just like Mega Latios). D rank has to go.
i think the point beyond that is that some of the mons we choose not to rank aren't unviable. they are viable if you know what you're doing. but the rankings should be mons that can actually be recommended and are somehow relevant in the current meta. which is why d rank is quite honestly a mess right now