I did it with Deimos lead and he trivialized some turns and fucked me over on others. Keep in mind Afla ignore defense and removes buffs with the single target attack that willalwayshit Deimos, whocannotguard because you're bringing him for the taunt, which lastsoneturn and requires bb/sbb.
He simplfies the fight in that youknowthe target of the nukes, so you don't need to write down other team members' stat threshholds. Without him, you write that shit down and guard with the unit with the highest attack, highest def, etc etc whenever one of those units gets targeted so they survive. Deimos won't survive, but he'll also be the only one to get hit. In other words, pick your poison, but be aware that the nuke is used five times iirc, so even on a perfect run all revives will be used on Deimos, who can't guard, if you use him. Again, simple, but adds five assured deaths.
I wouldn't use him as lead, though, because if I'm remembering the trial correctly you've only got one target the entire time and bb fill will be a massive issue, especially since the only bc on hit you'll be getting will go to Deimos, which'll screw your mitigator when you compound the lack of bc/bb fill lead with the fact that only Deimos will be getting bc on hit from anything that isn't aoe. Elimo can get away with that with her retardedly low-cost bb/sbb if you equip her with that sphere (forget the name, but it's a straight upgrade to evil shard), but that'll in turn fuck the rest of your squad because she doesn't help with fill rates at all.
So, no Deimos at all or Deimos without lead imo. I had to use Elimo to beat him, but I didn't have a mitigator other than Shera at the time, and my Shera was breaker, unsphered and died too much, but in your case I'd try to use Krantz and see if you can fill his shit up easily enough. Definitely don't do both Krantz and Elimo, though.
I did the trial pretty soon after 7 star units were released and it took a few tries due to Deimos shenanigans but ultimately I felt like the units I had outclassed the content. For you, it should be even easier, and for lead I'd do one of two things, and both exploit the fact that you have killer units at your disposal.
Option 1: Only 1 HP lead. Zeruiah + Haile leads. Acknowledge the fact that your units have much higher hp than intended for the encounter, forsake 1 of 2 possible hp leads and laugh maniacally at the fact that you have way, way higher fill rate than you're supposed to, as well as a unit that'll be close to SBB at all times because it'll be filled up and then partially drained. Or Haile + Avani for higher damage, first-class sparking, fill on spark and extremely potent and fill-friendly regular attacking. This guy fills your shit up so much as lead when you perform regular attacks.
Option 2: Haile + some sort of damage lead with + HP. Avant for lolz, Korzan for HP/bc on hit, whatever.
Either way, you have access to waaaaaaaaay more than I did. Think I did Deimos + Oguro or something because I didn't have much and both were new and shiny. And I'd probably fill the rest with damage subs and a mitigator and see how many thresholds you can skip. If I'm correct in recalling that there's only one enemy throughout, Hadaron if you have him should wreck the encounter.