You definitely want to build something around Skullcrusher. For now it doesn't seem like you can make an unkillable team, so you probably just want a classic 1:1 rotation. Ninja is a good choice for DPS, though he can make things a bit annoying to tune, so watch out - try to keep him as fastest so his A1 doesn't mess up your orders. Fayne is a good choice for the second DPS, since she brings all the debuffs as well. For Leech, Versulf works great, but, books are hard to come by, so, if you're short on those, Ghrush makes a decent choice too. Lastly, you need someone to deal with debuffs - unfortunately I don't think you can handle both the SPD down and the stun, so you'll need to compromise and just eat one of them.
Grizzled Jarl is a good choice for the debuff blocker. You'll need him to be slowest. On green, you'll eat the stun, and since Skullcrusher is red he'd be the main target, so you need to swap Ninja out for a red-affinity DPS such as Rathalos. On other affinities, you'll use Jarl to block the stun. So, all together, everyone should be between 170 and 190 speed, so that you can use the same team on UNM and NM.
1) Skullcrusher - second slowest
2) Grizzled Jarl - slowest, delay A2 by one turn against green and two turns against other affinities. On UNM, A2 opener against green and one-turn delay against other affinities.
3) Ninja - fastest, make him as close to 190 as the tune is able to handle. Probably around 185 is safe, but put the numbers into DWJ to make sure.
4) Fayne and Ghrush - order doesn't matter between #2 and #3. For Ghrush, turn off A2 and A3. He's only there for Leech.
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