A lot of you will eat crow when new trials comes and Zargabanzo makes everything trivial with his support.
I'm not mad I pulled him on some 'I wish I would have gotten Fryevia instead' shit (though I do) and I'm not going to delete him and I already levelled him to 100 and mostly max potted him and I'm using him and yada yada, but I just don't see it.
I'm trying to think of trial usage. He honestly strikes me best as a high HP tank companion. Throw up his 100% buff on the tank, tank gains enormous survivability, tank pops their provoke/cover ability. Rejuvenate will be great on a 7k+ HP tank. You can roll party buff inbetween, and pop Word of Law for threshholds if you don't have something better available.
My question is, in this example, what is my team and how much benefit am I deriving from Zargabaath? I still need a party healer. He can't clear statuses or revive. So I'm bringing a tank, a healer and Zargabaath. If my tank is Wilhelm (or Cecil?) I need a breaker; if my tank is WoL I may not. If the trial is completely immune to breaks then it's fine.
I'm at 3/6 units now. Am I bringing Rikku? Hyper NulAll removes two of his selling points in one cast (though with a turn of setup) as well as her LB. If the trial is one that requires or even greatly benefits from Reraise antics, then I need to bring her. I'm at 4/6. Those last two slots are probably getting filled with damage of some sort, since none of the above units are going to be doing any.
So let's look at this example team. I'll even stack the deck a bit in his favor and make our healer Y'shtola instead of Tilith. What am I getting out of Zargabaath?
Rikku has stronger damage mitigation and an equal elemental res buff. She can revive and (with her LB) provide higher DEF/SPR numbers than Zarga's group buff, in addition to the reraise component.
Y'shtola has group heals, status heals, raises, a single-target full-heal (that does not restore MP, to be fair), and a powerful damage reduction on her LB (far from reliable, though)
Zargabaath's contributions, then, are spammable damage reduction (in case you reach a threshhold/turn count with Synthesis dropping or no Y'shtola LB available), Rejuvenate's MP restoration (which is useful on no-item missions and less meaningful otherwise; when's the last time you used 5 Elixirs in a trial?), and stat buffs.
They're big stat buffs. The biggest we have access to currently. That's good! And Archadian Light is all of the buffs in one, which helps turn economy (you'd otherwise generally need two actions to cover everything unless you are bringing Tidus, Tilith, or, uh, Rain?). That's also good. And Hero Crest is really good if you can cycle it on your chainers or keep it on your tank.
But... that's kind of it? His primary contribution is stat buffs. There's not really any getting around that. It's the first ability he learns and the last one he learns. His damage is pretty minor. He has no innate provoke, though good-to-great survivability. No, Golem's provoke isn't a serious option anymore.
He's a trial smoother. He can do various things that take the turn stress off of your healer or support so they can do something else and everything runs more smoothly. But he can't replace a healer and he may or may not be able to replace that other support. Worth a unit slot? If it gets you the kill, hey, I guess so. Worthy of being a 5* base that seems to have displaced a powerful capper? Gumi seems to think so, at least. I'm skeptical. But willing to be convinced otherwise.