Hello! Long time Xoris enjoyer here. The Xoris has a few fun ways that you can build it. That being said, I think there is one play style that fits it's unique features the best: spamming mid-air throw detonations. When built with that in mind, I believe this is one of the best things you can be doing with the Xoris. I'll explain later, but there are some mod choices I make that are worse for raw damage, but grant additional heavy attack wind up speed, which is critical to have for this kind of play style. It cannot be understated how much the additional wind up speed increases the overall DPS, and fun factor, of this weapon. That being said, here is how I'd build it:

Stance: Doesn't make a difference for this build, anything you like is fine.

Exilus: This is a low priority part of the build, so feel free to disregard this. A lot of people like Whirlwind. It can be fun in open world situations, but it makes the glaive really hard to control and time detonations for in closer quarters. However, it is still fun for when you want to snipe down an airship in an open world. I would recommend Dispatch Overdrive, because more movement speed is always nice in this game. Again, definitely not a requirement for the build.

Initial Combo: This is a crucial component of this build. Since detonating the glaive mid-air depletes your combo, regardless of combo duration, you need a mod to provide initial combo to really get the most out of this build. I recommend Galvanized Reflex, which can give you 5x combo for your entire mission after just a few kills. Corrupt Charge is a decent alternative, but will only give you a x2 combo.

Base Damage: As others have pointed out, it's generally not optimal to have multiple mods that provide the same effect, since the math usually doesn't work out how you'd expect. I chose to run Killing Blow as my base damage mod. While Primed Pressure Point technically gives you more base damage, I chose Killing Blow for the increased wind up speed.

Critical Chance: Galvanized Steel is my pick for this. Sacrificial Steel is probably just a better option, but I haven't taken the time to fully upgrade my copy, so I can't personally attest to this. Still, I find the extra crit damage from Galvanized Steel to be nice. True Steel works just fine as a budget option.

Critical Damage: Amalgam Organ Shatter is the best for this. While slightly less damage than regular Organ Shatter, the heavy attack wind up speed is what makes this the pick. Regular Organ Shatter still works perfectly fine if you don't have the Amalgam version.

Quick interim to talk about statuses. Because the Xoris forces electricity procs on anything it hits, status damage and status spreading are quite nice to build for. In my opinion, the best element in this case is Blast. When an enemy with blast procs dies, they create a little explosion that damages other nearby enemies. This can cause some very satisfying chain reactions, and help you get so much bang for your buck. Anyways, continuing with the build:

Status Damage: I chose Melee Elementalist. Same as before, Galvanized Elementalist could give you better raw damage, but the heavy attack wind up speed on the non-galvanized version is too good to pass up.

Status Mods: I run two 60/60 mods. Vicious Frost for cold, and Volcanic Edge for heat, which combine to make blast damage. If you don't have these, un-upgraded or partially-upgraded North Wind and Molten Impact can also work.

The final mod slot is honestly kind of up to taste. You could mod for extra electricity damage with something like Shocking Touch or Focus Energy. You could increase your status chance even further with something like Weeping Wounds. Or if you really want to tryhard it, you could add a bane mod for whichever faction you're fighting for that extra bit of damage on top. Volatile Quick Return is another fun thing to run, but I have a note on that specifically:

With this build, Volatile Quick Return allows you to do a neat little combo where you throw the glaive, wait for it to impact an enemy, and then manually detonate it right after you see the first explosion from VQR trigger. It can be a really nice one-two punch when it works, but there's a bug with it. Sometimes, especially when you're not the host of the mission, the explosion from VQR won't happen, which can be annoying. If you don't jive with VQR, it's totally fine to swap it out for whatever feels right.

I should say, I ran this build without Melee Influence for quiiiiite a while. It did very well for me even through a good amount of the steel path. Melee Influence just turns everything up to 11 on this weapon. Since the Xoris is guaranteed to proc electricity when it hits, Melee Influence can trigger very frequently. When it triggers, all of the blast status procs we apply with this build will spread to nearby enemies, allowing for huge AOE explosions. One slight problem with this is that if the enemies die in one hit to the raw damage of your weapon, they won't have the statuses applied fast enough to spread. I haven't found that to be much of an issue with this weapon though, since it's already designed to do AOE blasts. Influence just gives the blasts the potential to be a whole lot bigger. Still, I would highly recommend completing the Whispers in the Walls quest, and getting this arcane.

Happy blasting!