-Shard bombs are still good with masses of mobs.

-Electron Vortex is only good because it shocks the mobs and keeps them huddled together (Making it good for that Shard Bomb, eh?)

-Mad Bomber Helm and Volcanic Demo Suit. You still get max CTR and med damage also.

-Two Bomb damage trinkets (To make your overall bomb damage Max!)

-Shiver is nice to have, but I'd prefer Venom Veiler because it lowers defense and attack. I think VV is a better support bomb than Shiver. My opinion.

New Sun Shards isn't all that great since the update, due to the explosions flinging enemies around; I'd leave it at the 4* version for the moment. Dark Briar Barrage is generally a better option, piercing-wise, and covers a much larger area, being efficient against gremlins as well as beasts and fiends.
Nitronome is a good basic damage choice for bombs. Go for it.
I personally find Shivermist Buster to be a bit of a pain sometimes, since I frequently encounter people who like spamming the bomb. This would be good, if they didn't freeze enemies in my face and restrict my mobility as well if I'm not careful. It's alright if used carefully, but I find Voltaic Tempest and Stagger Storm to be more party-friendly movement-restricting options, since they don't prevent you from shieldbumping enemies away all the time the status is active. Voltaic Tempest can also rack up quite a bit of damage on clumped enemies, particularly zombies which tend to move fairly slowly.
Shocking Salt Bomb is probably the best of the available shard bombs; the shock status is well worth the loss of damage, since it restricts movement and prevents enemies from being knocked around so much.
Electron Vortex is generally considered a better choice than Graviton Vortex, if only for the shock status preventing enemies from being flung about so much once the bomb expires. Both are great party options, though, and work well with shard bombs.
You might also wish to invest in an Ash of Agni and Venom Veiler; the latter is extremely helpful with large numbers of healers around, or in order to limit damage that bosses can deal, and the former works well synergistically with poison. If you have to get just one, though, I'd go for the Venom Veiler.

And yes, Volcanic is probably the best choice unless you decide you don't care about statuses any more because you love remedy pills so much... in which case, knock yourself out and get a Chaos set.

add Operation Crimson Hammer while you're at it. You can buy it from someone else (around 1.5 k CE I believe) if you're using steam. Dark retribution is one of the best dps bombs at clockworks.

Your armor set could be these beside of those general bomber.
Black Kat Cowl, Chaos, Mercurial Demo.
Trinkets most likely are just either bomb damage, ctr or health pendant from those krogmos.
(or may be status effect resistance you hate the most?)

Personally I really want to try Black Kat Cowl + Chaos Cloak + Damage Bomb Trinket + CTR Trinket + Bombs UV CTR Med.
Those will get you movement speed: med, bomb damage: max, bomb ctr: very high (max with bomb uv).

Are you interested in Kat Hiss Cowl? I have pages left after the event I don't really know what to do with. If you're willing to pay for unbinding the 3* hat I should be able to hook you up with what you need.