I'm a bit confused on team building, so in this image it says the top DPS vs red it says Akari is the top choice, with Aru as alternative, and then Haruka down there as filler AOE and Serika as AA, which I don't know what that means. I also have Yuuka who I love.

If I look at the JP tier list, Aru is way above the other units. So is this a single unit vs team comp kind of deal? I wanted to swap Serika or Akari out for Haruka since she's higher up on the tier list, but she's a tank, so I'm not sure if I'd have to swap her out for Yuuka which wouldn't work for me, or for another DPS