Krell seemed pretty strong.. In sabers only I'd give it to the duo. Thing is, Dooku probably has a big force edge on Krell, and I could see the count dispatching him with the force when he gets pressured too much in sabers, like he did to Kenobi in RotS. It's very close, the arena is an open space so I guess this would favour Dooku the most, allowing him to retreat more easily and TK or shoot lighting at them. In this scenario, I'd give it to Dooku 6/10. If they fought, like, where Dooku vs Savage/Ventress happened, I can see the duo winning