I'd say Musashi deserves that spot if you're talking about just her one on one duelling capability. She doesn't work amazingly well in teams, though- unless the team's focused on supporting her, she's almost better off alone, and she has absolutely nothing that helps any teammates, but then again if you added a taunt or star gen/attraction to her kit she'd be even more broken than Waver/Merlin, in a way.
Marie gets about 5k damage per hit, on stuff she's strong against. IIRC, Kiara was getting something like 20k+ per Arts.
Isn't 99% of the game's content farming?