An idea for Salter team comp

I highly doubt it. I think it MIGHT be possible, but it would be a lot harder than setting Asterios up for Goetia. The difference between Salter and Goetia is that Goetia has insane hitcounts(and he hits AOE, so less rng reliant). Asterios really depends on the np gained from getting hit to build his np up and with Salter only hitting 1-3 times and mostly not hitting him, it’s gonna be hard to loop his np reliably. With Goetia though, his insane hit counts and Aoe basic atks leave nothing to rng and Asterios is hit with everything, gaining lots of np. Not saying it’s impossible, just harder than it would be for Goetia

To add to Eragon's answer above, Salter crits very hard and buffs herself often. She also stacks debuffs like crazy. Without a debuff remover, a defense buffer, or a healer, all that damage will accumulate too fast near the end.

2-3 GoA will heal 2-3k at minimum (depending on NP level) but Salter can hit harder than that if she goes crit crazy, which happens more often than we'd like, so that's a negative net). 2 stacked Chaos Labyrinth is -40% attack (-80% the first turn after it is used due to the interlude) but, other than that, a Merlin + Asterios party lacks Def up skills to make up for the Def debuffs during the second and final bars, all of which will be focused on Merlin.

You've mentioned that you used Merlin's Hero Creation as an emergency heal. But that was in addition to David's second skill (party Evade and heal) and having 4-6 GoA active to heal 4-6k per turn at minimum (which I assume is due to David having more Arts cards than Asterios for Arts chains). David's NP also has a chance to seal Salter's skills, meaning there's one turn where she might not buff her attack or crit chance.

The fight will also last much longer due to the difference in damage. Asides from the difference in base stats, Berserkers have a x1.1 multiplier and a further x1.5 due to class advantage. (x1.65 in total). Archers have a x.95 and x2 multiplier for a total of x1.90. In addition, Archers have higher star weight to take advantage of GoA's crit stars (Berserkers have lower star weight than Casters). Even with Labrys, that would only be a 1 turn damage steroid for Asterios so you may have to choose between using it immediately or waiting until he can make a Buster-crit chain to go with Hero Creation (if you aren't saving it for an emergency heal). NPs are also in favor of David due to being ST.

This is all based on what you've mentioned of your fight and not meant to discourage you or put your idea down. It might be possible, especially if RNG is on your side and Salter doesn't crit one Merlin three times in one turn, but I think it would be a LOT harder with Asterios than with David.

I used David / Tamamo / Merlin (support), no one died. I used Fox Wedding as cure skill, the second effect of the David's NP to avoid Salter's charge gauge skill.
The skills of Merlin and David to avoid Salter's NP or let merlin/Tamamo recuperate some healt.

i clear with Mash, Waver, Merlin after gil and waver (support) die in 2nd break.

My team was Gil, Merlin(10/10/10), Waver (support), Waver(4/4/6), Mash(10/10/10), Archer Altria. But end up both Gil and waver are gone after a NP. Then Mash, Waver and Merlin just grind Salter for about 2 hours. I use Atlas institute uniform lv 1 for this run. Just make sure Mash HP is full all time as she can take a Salter's NP without dying. Salter will target any caster class first so mash is very safe unless you use taunt. If my waver's skill is max out then will easier. With Mash skill 1, NP, and waver's skill 2, Salter cant deal much damage. Just keep spam NP for Waver's and Merlin as much as you can ( Salter got 3 stacks of curse most of the time).