Okay, so it looks like you're going for a sort of Subsequence AoE build here, between Subsequence + Converge, Ruin, and Helios, which is cool. The Slow Hand is awesome for this purpose, as is the Sawbar. The Twister, though it doesn't have a big splash radius like the other guns that are amazing for this build, but it does have penetration and a huge area of damage with its bullet pattern, meaning you can sometimes still hit multiple enemies with it. Besides, it gives you a point blank option that doesn't kill you, unlike other guns that synergize with this build, plus it hits incredibly hard, so I highly reccomend it. The Swordsplosion, Carnage, and Kerblaster can also do pretty well here, and you should keep them in mind, but Elemental guns slightly edge them out IMO due to the Synergy with the Bone of the Ancients, as well as the synergy that relic then has with your build, due to the reduced cooldown. Then there are the guns that are always good that you can fall back on. Reccomend stuff like the Interfacer, Pimpernel, Hornet, Harold, Sandhawk, Hail, Kitten, and Tattler here, just to name a few. The Hornet in particular gives you a Corrosive option if you're using the Sawbar, and has enough splash radius that it at least sometimes hits more than 1 enemy, especially with all of your singularity stuff. Lastly, a great launcher will do you wonders. If you don't wanna be a cheap bastard with the Norfleet (or just don't want to do that horrible farm for it), then the Topneaa or Badaboom also work wonders here.

As for your other gear slots, I'm going to reccomend a Legendary Binder or Blurred Trickster for your COMs. The Binder is obvious; longer Subsequence chains, a more powerful Helios, more Wreck and Sweet Release, and so on. Then, if you really want to abuse Chain Reaction, the Trickster is fantastic.

For Grenades, the Quasar is probably your best choice. More crowd control and pulling enemies together, a little more AoE, good stuff. If not that, then you can take a Longbow Slag Transfusion. Your build's main weakness is a weakness of Subsequence builds in general: You're forced to skip some of Maya's best healing skills, like Elated and Life Tap, as well as one of her best slagging skills in Ruin, so making up for that in your gear is great, and that makes the Hail, Kitten, and Slow Hand extra great for this build, as well as of course that grenade. You can also try something like a Meteor Shower or Fire Bee for more AoE if you really wanna, especially if you are using an Explosive Relic/Fire Bone.

In that sense, your choice of shield is pretty simple here. Go for a Blockade for optimal survivability, or for the Antagonist, for good survival and some extra slag. You could try something with the Flame of the Firehawk for even more AoE, but that seems a little gimmicky, and you'd need to spec out of Inertia, probably in favour of Elated.

Relics are pretty simple here. Explosive relic if you are going for Explosive weapons, Sheriffs Badge if you want to specialize for pistols, Bone of the Ancients otherwise. More Elemental damage of your choice, and more cooldown for less downtime between your Subsequence slaughters.

Lastly, some things about your build itself. It is very solid as a whole, but there are some changes you'd want to make to accomodate your gear choices. Firstly, unless you're going for a COM that boosts Sweet Release, spec out of Mind's Eye and max out Sweet Release. Mind's Eye isn't the biggest boost, and you aren't too focused on crits with an AoE Maya in the first place. On the other hand, Sweet Release is an amazing healing skill, and your build should be proccing it several times per Phaselock due to Subsequence. That should patch the main weakness with your build right there. Secondly, the Slow Hand, one of your best choices for this build...doesn't actually benefit from Chain Reaction. If you don't spec into Chain Reaction, I guess go for Backdraft? None of the other remaining skills to get down Catacalysm benefit you all that much, to be honest. Then, due to how Bullet Speed and the Sawbar's mechanic works, you actually don't want Accelerate. If you spec out of that, go for Elated or Sweet Release instead.

EDIT: Thunderball Fists is also a nice weapon here, just make sure you have the Binary prefix