What the hell is this? Dooku has never had any trouble facing two opponents at once. In fact, I'd say he relishes under the assault of two foes, given his performances against Obi-Wan and Anakin in S6 and RotS. I say he eviscerates Shan with absolutely no difficulty at all, and then deals with Malgus using his superior swordsmanship and unarmed skill.
And if we factor in the Force, he'll probably just one-shot Shan and proceed to ragdoll Malgus.