Heres the thing and why saying something is OP on beta makes 0 sense because A. Its actually Affliction that is outperforming Shadow on Beta and B. Not only has Tuning not happened yet but there are legit specs(like outlaw) that are still missing talents. Go for playstyle, not Numbers.
With all that being said i would compare Affliction to Shadow in the Same way i would Compare Destro to Fire Mages. Yes they have some DoTs but they are fundamentally differently.