I really think Metagross should stay in D Rank.
Despite it having a good Attack, that means little when both Jirachi and Bronzong outclass it completely as a Steel-type who can tank hits from Dragons like Kyurem-B. It does have the tools needed to perform, but to use them is more trouble than its worth most of the time.
I dunno, maybe I just can't use Metagross properly worth spit. He's my favorite Pseudolegendary, but he's still a very mediocre Pokemon at any rate.