So I have been bringing CG/Seaside Nichol to the latest trials, and I've noticed that they do really well with finisher based teams. They can chain together, imbue, and with all their buffs active, it makes it pretty easy to survive even the hardest attacks by the latest trial bosses.

IMO one of the biggest challenge using CG/Seaside Nichol is that he has so many things they need do. They have to keep up the buffs, elemental resist, and if necessary act as an mp battery...etc By bringing them both together, they can focus on their unique skills or they can cover each other's defensive buffs should something goes wrong with either one of them.

The Rotation

The standard rotation is fairly simple. CG Nichol uses his buffs mitigation/elemental buff, and Seaside Nichol uses either MAG/PHY mitigation skills depending on the fight and the tank you are bringing. You can also give cowered courage to your debuffers/tanks to further free up Seaside Nichol. Seaside Nichol spams the LB as often so he can to keep the 3000HP barrier and high defensive buff up while CG Nichol applies elemental buffs, imbue, mp battery..etc, and keeps his LB for emergency buffs. With double Nichol setup, you have elemental resistance buff to Light/Dark/Fire/Water/Ice, as well as multiple sources of debuff removal. Once you have all defensive buffs applied you should have 170% DEF/SPR buffs, 3000HP barrier, 30% general mitigation as well as 30% PHY/MAG mitigation. Even if Seaside Nichol's LB is somehow gone, You should have 150% DEF/SPR buffs with 1000HP barrier all the mitigation skills available to you. Also, if Seaside Nichol is removing buff on that turn, you can use CG Nichol's Forutne/Courage stance for better buff and hp/mp regen without suffering any setbacks.

Once the buff is applied and your finishers are ready, you can have them use Flood chain skills and cap it with your finisher. If you want extra flexibility, equip Leviathan on your healer or debuffer and they can build chains while one of your Nichol can apply buffs or do whatever else is necessary for that turn.

VS. Gilgamesh

For the fight against Gilgamesh, my team was CG/Seaside Nichol, Merc Ramza(Full Evade, Aqua Blade Necro Dagger), CG Lid, Balthier, friend Balthier.

In terms of offensive strategy it's basically the same thing as what u/Lohruk did. You just wait until you can kill off Gilgamesh with a good roll on Balthier's rapid shot. With all the defensive buff, I didn't really need a dedicated healer, and occasional Curaga from Merc Ramza was more than enough. The double Nichol setup can also expedite the process by imbuing Balthier(s) if he has rapid shot ready for the next turn after trick shot, and they can also help build chains for Balthier too.

VS Asura

For the fight against Asura, my team was Ayaka(6 star) CG Nichol(Galkan Dagger for sealing Earth), Seaside Nichol, CG Lid, Balthier, and friend Sieghard(Full Evade)

For the Asura fight, I decided to go more defensive and brought a healer in place of a second attacker. Again with all the buffs up, it was actually difficult for anyone to die in the fight. There were sere several instances where counters from the tank triggered the powerful retaliation move. That move would usually wipe out my team, but with Seaside Nichol's LB all other buffs, they survived very comfortably. The fight after the 20% threshold wasn't that big of an issue either, because even when my tank died, the rest of the team was able to take the hit while I revived my tank.

Pros&Cons of the setup

IMO the biggest pros of this setup is flexiblity and redundancy. Between the 2 Nichols and Leviathans, you have 3 units that can build up chains, and you also have the option not to run Leviathan. If you put Leviathan on your tanks/breakers, they can cap chains on their free turns without worrying about your supports taking time away from support duty. You also have flexibility to respond if one of your chainers needs to take emergency action for that turn.

It also gives you a lot more equipment flexibility compared to using Pod chain. Usually, you need to bring matching set of weapon for your supports if you want to element chain with them and give up 2 equipment slots, but with this setup you don't need to do that and just give them LB up gear instead.

The setup also makes your attacker bulkier. Personally this is a big deal, since most attackers tend to be pretty squishy. With this setup you don't have to worry about your attackers dying while they are working through their rotations.

The downside is that this setup is locked to water element for chain building, and without any outside source of imperil, you are looking at 50% Ice/Water Imepril from seaside Nichol.

Conclusion

The introduction of CG Cid, enhanced Balthier, people have started exploring the single finisher DPS option, and it has created more flexibility from the traditional 2x chainer team comp. CG/Seaside Nichol seem to compliment the finisher setup really well due to their built in kit, and it allows supports to have redundancy, as well as being able to specialize in certain aspect of their kit without being overwhelmed.