Notes:

Smogon's University Twitter page.
http://www.smogon.com/forums/threads/np-oras-ou-suspect-process-round-3-ghosts.3533937/
“After removing from the metagame numerous offensive powerhouses, we realized that the time had come to invert the course. Presently, the OU metagame is stale and the abundance of defensively oriented teams led us to believe that a mixed attacker with great defensive and offensive typing will probably give back some vivacity to the tier. Right at the beginning of the X/Y era, many people suggested that Giratina-Origin shouldn’t have been included in the initial banlist. Its base statistics are on par with those of several other Pokémon who characterize the current OU metagame and the fact that it’s forced to run Griseous Orb makes Giratina-O a relatively predictable threat. Likewise, according to top players of the caliber of gr8astard and McMeghan, Giratina-O’s 150/100/100 defenses will help balanced teams deal with threats such as Charizard-Y, Landorus-I and Serperior.”