I wouldn't say it was dominated by Marnie since there are no data that proves it. There is also the fact that she's a Premium unit so there isn't widespread use and the whales will whale with their Black units. Waltz is actually a popular Dancer, contrary to some beliefs, since she's offensively oriented and the duration of her skill allows other units within her range get as much damage out as possible with their skills. Waltz is also an event unit, which meant that anyone who was around for her event, is able to use her.

Dancers are good as long as the team lineup works around them. Hana and Marnie are often used for their repeated use while Waltz is used for the higher burst (melting bosses).