You need someone with good waveclear to be able to do this quickly, and ideally someone who can do it for both waves. Rathalos is a solid choice there. I'd probably drop Ronda and Scyl, and replace them with Rathalos and Robar. Between the two of them you should be able to clear the first two waves easily, and then once on the boss, the two Coldhearts should make short work.

You're gonna want to put Coldheart in survival gear like HP% and DEF% Chest and Gloves. Also you should only need to bring one but that's beside the point. Given your roster and since you built 2 coldhearts, here's what I'd say:

Farakin, Coldheart, Coldheart, Nekmo and Wukong. Nekmo in lead. Nekmo controls waves and Wukong does great AOE damage with A2 and A3 on trash. If you have Deacon somewhere, swap him with Nekmo since he does AOE decrease defense. When you get to FK, he shouldn't be able to take a turn and you should be able to full auto it by setting abilities like Farakin's A3 to "Do not use" on Round 2. Once FK's shield is gone, rotate the Coldheart's A3 to keep wiping out his turn meter. With Nekmo's turn meter boost, increase speed and decrease speed it should be really easy (also turn off Coldheart's A2 on Round 3)