So I crafted all of them, and I tested each one, and here are my thoughts on the balance of each:

Normal:
In direct competition with: Nitronome and co + damaging haze bombs
When compared to Nitronome and friends, it is almost entirely sub-par, being that it deals far less damage. However, it isn't always as obnoxious, and it is slightly safer due to its lengthy detonation time. Haze bombs offer a much better alternative for this however, being that they are capable of dealing damage over an area for an extended amount of time, making it easy to actually hit with them. Overall, this bomb is much harder to use than either the haze bombs or the blast bombs- and doesn't pay off for it very well.

Piercing:
In direct competition with: Dark Briar Barrage + each other
Overall, dark briar barrage is the ultimate solution due to its ability to flinch enemies easily.. it also does more damage, and is easier to use…. oh, and because of its ability to flinch enemies, it is also better at everything else. Compared to each other (and disregarding the negative effects of stun), the new RSS is almost entirely better, with the exception being in places where beasts are the only threat.

Shadow:
In direct competition with: Graviton Vortex + Dark Retribution + each other
Dark retribution is primarily best for the reason that it is capable of dealing killer damage to turrets as well as the fact that it has higher overall DPS to other slimy/gremliny mobs. Graviton vortex is a terrible choice for DPS except against gremlins, in which case it is still fairly bad. Compared to each other, the shocking salt bomb is far better than the deadly dark matter bomb, except when fighting only gremlins and nothing else due to gremlin's resistance to shock.

Elemental:
In direct competition with: Electron vortex
Electron vortex is huge as a utility, and as I've written before, possibly the strongest bomb in the game. However, it falls short to the offered shard bomb safety mentioned under normal, making the deadly shard bomb better than it as a pure DPS weapon… that being said, nitronome will still out damage it against everything, and dark briar barrage is still far better than it against undead.

Whats wrong with this picture?
First and foremost, is the damage. In each example, the damage dealt is simply inferior to the other options. There is never a situation that brings me to say "man, I wish I had my deadly shard bomb instead of this ash of agni!" because frankly, I'll always be better off with the fire damage. Another thing is that they often conflict with one another… that is to say, that there is never a situation when I say "man, I wish I had my dark matter bomb instead of my slime shocking bomb for this gremlin+slime level" It is unreasonable to expect players to craft a dark matter bomb JUST so that they can have a superior shard bomb for deconstruction zones and other pure gremlin areas, as the shocking salt bomb is close enough to making it.

What could be done to fix them?
There are several solutions that I've thought of to this, depending on the intended role of the bombs… one uses nitronome much different than ash of agni. With nitronome, you want to stand in the middle when it goes off, with ash of agni, you want to dodge and cover ground. I've 3 strategies towards fixing them: Drop+Strafe, New and Improved and The Damaging Support.

Drop+strafe!
Currently leaning more towards the ash of agni style of bombing as well as the current usage for the bomb, a damage buff and knock back reduction buff would alleviate the conflict that the bombs get into with nitronome/dark briar barrage, and would provide a more standard bomb approach to the problem if running around and covering ground. This option favors making it just… better, so that it can compete with the other bombs.

New and improved!
Alright, get this:
-Add to the fuse time that it takes to blow up as well as the fuse time on the crystals
-Halve the time it takes to charge the bomb
What do you have? More potential for damage per second, and a harder to use bomb. Why is this good? Because it merits skill, and I'm all about that. Why wouldn't you want it? Because it creates a new pattern of attack- that relies on the bomber constantly dropping bombs on each other's edges, and that could mess with the party a bit. Removing the knock back would overpower it, but that isn't such a bad thing.

The Damaging Support!
Leaning more on the "use bombs as support" and "teamwork" side of things and less on the "KILL EVERYTHING" side of things, we have:
-Greatly increase potential to stagger enemies into not attacking
-Reduce charge time by a small amount
-Reduce fuse time on the shards once deployed.
-Reduce/nullify the knock back given by the shards when detonated
What does this do for it? Lets the bomber help her team by staggering enemies! This will give it a new edge of safety, while keeping it low on power. The charge time reduction given here would also give it a slightly higher base DPS, which is somewhat needed for them to live up to their name…. but won't make them anywhere near as strong as other items in terms of raw power.

Compared to each other…
These fixes don't address that. If we want them to, then we'll have to do something about it. The obvious fix for it is to specialize the bombs some how, that is to say, that the dark matter bomb should hold a different niche than the salt bomb. An easy fix for this would be to make the deadly dark matter and deadly splinter bombs into beast/gremlin killing weapons. That would put them on par with the others, and would give players a reason to make them.

The other solution that I can think of is to make them deal split damage- although you, the developer who so selflessly reads this, probably won't like that idea so much due to the whole "no moar split damage" thing.

Finally, they could be made to occupy the same roles as dark briar barrage and dark retribution, albeit with different attacking styles. This would be done by changing the damage output to be a bit larger than their counterparts, the scintillating sun shards and the shocking salt bomb. I would go for 23 percent less damage, as that is less than the place needle compared to the blitz at ~30% (which is not a good example of separation of roles) but more than they are currently separated by, being ~12%.

Now go post about pets and cover up my thread so that my ideas will never be heard.