Just wanted to say one thing about terrakion.
I think we all put it on S-rank because of how scary it was during the bw1 era when it could get 2 or 3 kills at time, and basically battles often were something like "who kills terrakion first won".
Now battles are not this way anymore. The classic volturn sand consisting of Celebi/rotom-w/scizor/terrakion/landorus/tar is not common anymore. Why am i saying this? because that was exactly the type of team that could let you overkill everything with terrakion.
An example to make it clear: you have celebi in, your opponent has politoed. its probably going to switch out on ferrothorn so you do u-turn with celebi. At this point you send out kion and you have a cb kion against a ferrothorn. You know you have the advantage now, and if your opponent sends out a fight resistor you can cripple it with stone edge 2koing it. It was basically a free kill for you.
now it probably wasnt the best example, but wath i was trying to say is that terrakion was once scary because all those volturn cores let it always have a free switch in, and basically always on a favourable condition for you, letting you decide the game depending on which stab move you click.
Now, those days are gone. This type of team isnt seen anymore. A lot of sand teams prefers keldeo instead of it. Just think about how many tyranitar runs a choiced set nowadays, and guess what? tyranitar always had stealth rocks in the past, now most of the time its terrakion that does this role, because pursuitting ninetales and politoed is more important for tyranitar rather than setting up stealth rock.
The fact is, terrakion its a good pokemon, surely A-rank, but its not as scary as it was before. The Choice band set doesnt work anymore because volturn cores are not that common now, and if you are using it on an hyper offensive team you may be better using a life orb double booster set, because locking yourself into a move can be a loss for you in this metagame. Boosting sets works sometimes, some others not. Terrakion simply doesnt force as many switch as before and his typing isnt the best defensively - it surely has a good bulk, but not many resistance to setup freely a sword dance or something. In top of that, remember that its week to ground, water, fight, psychic and grass moves, which arent exactly as common as poison or steel.
The focus sash set its good, but people needs to realize that it was good for the surprise factor months ago, now if you see a terrakion lead you know for a fact what it will do. And this role its one the best to give to terrakion at the moment, even though it faces stiff competition from azelf and aerodactyl (yes, speed matters)
The choice scarf set its good, probably the best set to use thanks to his stellar speed and the fact you can hit everything for neutral damage, but thats it.
In top of that, breloom and landorus-t drammaticaly raised in usage, which makes things even harder for terrakion to shine.
Now, i want to stress that i do not think that terrakion its trash, i just mean that S-rank is for things that we actually want to be banned, and terrakion isnt really the case.
Ps. i dont know if its just me, but every time i do a sand offense team with terrakion i always end up with terrakion being the "weak link" and i always remove it for something else. it doesnt matter much with his status, though.
Pps. oh, i forgot that it was also one the best offensive check for genesect, which is now uber, maybe this was one of the reason it was so hyped?