ok lets review
D Rank: Reserved for Pokemon who are simply not very effective in the current metagame.
this pretty much describes volc
in a hazard centric metagame with no reliable way to spin, volc really is ineffective
unlike ho oh who shares the x4 sr weakness, he does not have regen or an amazing stat distribution
compared to reshi, he has a greater sr weakness and doesnt hit nearly as hard, only boasting higher speed and quiver dance
unfortunately, his bulk is so terrible setting up is ridiculously difficult
bug STAB may seem cool with stuff like darkrai and mewtwo running around everywhere, but reshi can ohko them anyway even without boosting
252 SpA Reshiram Blue Flare vs. 4 HP / 0 SpD Darkrai in sun: 387-456 (137.23 - 161.7%) -- guaranteed OHKO
252 SpA Reshiram Blue Flare vs. 4 HP / 0 SpD Mewtwo in sun: 387-456 (109.32 - 128.81%) -- guaranteed OHKO
sure it can do some cool stuff like ohko 252 arceus, but after sr, most variants of volc are ohkoed by espeed
i honestly dont think he deserves to be ranked, but d is most fitting
ps: heres the research week they did for it
http://www.smogon.com/forums/showthread.php?t=3466936