The monk might not have the same potencies, but the monk does have extra damage from GL, Fists of FIre, and Twin Snakes, whereas Rogue only has Venom, and that's all she wrote outside of cooldowns. Monk also has access to 30% crit bonus from Internal release. Monk also has much better access to defensive utility--if things go sour a monk has quite a few ways to stall while the healer rezzes the tank. The Ninja can... use worse versions of the Monk tools. On the other hand, Ninjas have superior offensive utility, and that's cool.