The Problem with Tortofists is that they are incredibly unpredictable compared to everything else.

What needs to change is:

A Fixed drop pattern (like the current shard bombs they would always try to form a set pattern when they land).
A drop indicator that shows the knight holding a tortofist charge where it will land.

Actually, the gun is fine as it is right now. IF you want to 'fix' it, you would either destroy its purpose or you would make it be another imbalanced weapon - and tortos are by far my favorite guns.

You say the crystal drops are random? I say the direction of alchemers are more random. Yes I mean it; you can argue that it always turns left, but you can bring in similar arguments to the location where the torto shards come down - with ofc a certain RNG - but by far not as random as you want to make it, once you know why it is landing on which location for what reason.

You also do not need an indicator where the crystals come down, just learn the distance.
Example: Antigua-line guns always have the same range. What people may not know is that the antigua bullets create an impact when they reach their limit and disappear. This impact is able to get rid of these flat plants that can drop hearts or crowns. Just walk through a Lichen level and try to destroy all these plants with a specific gun only - this is the best way to get familar to the very exact range of your gun.

Killing randomness completelly is killing efficiency.
It is a big deal if you have a fix pattern or the possibility that many torto crystals end up very close together and 1hit a Trojan. If you have a fix pattern then this pattern will definitelly cover a larger area and less crystals hit the same enemy. Result: enemies that you can 1hit with the current mechanic are impossible to 1hit after this messed up idea.

Instant damage without delay?
If you want to deal instantly big damage without delay after you released your charge attack, then Tortoguns are the wrong type of weapons to you; just pick your combuster and waltz through the enemies or pick your Needle for that purpose.

Tortoguns are agile guns that offer great flexibility combined with high damage numbers - but this is traded in for a higher grade of skill level that is required here and also at the cost of a quite high delay after releasing crystals and actually dealing damage - but you know yourselfe very well that there are situations in whose you want to deal high damage by having a great distance to the crowd that is fallowing you, maybe even with healers between.

In this case: Pick your Tortogun and nuke them out of a safe distance as how this weapon is meant to be used.

1. Knowing where your bullet go:

In Spiral Knights this is all about getting familar with your weapon. Otherwise e.g. the Alchemers would much more benefit from this since they shoot zigzag counterclockwise ricochets or the Autogun so you know how many bullets will hit your target if you unleash it.

2. Missing your target.

Sry if autoaim does not help here, but serious, if you miss a target again and again then practice your skills.
For the start I recommend to keep high distance, unleash the crystals and then rise your shield and walk just in front of the shard field. The enemies will come close and stop right at the incoming crystal area while preparing to attack you - a preparation that will almost never gets finished.

When you can handle this, then try to use that tactic in mid combat. but instead of high distance, you move a circle and froce the enemies by knowing their AI to end up below the crystals when they income.

And after that, you can increase the damage to push enemies back into the crystals after they got blasted out of them by the crystal's impact. To me, Using tortoshields worked best for that purpose.

3. The purpose?

OHKO? CC? Something totally new? It depends on how you use it. But it is surely a great weapon if you are beeing chased by a large group of monsters and need to decimate their number while having no interest in jumping into the monster pool and get surrounded. I can't say if it is intended that you can OHKO stuff, but you definitelly can with skill and that is the potential I love with these guns. Rendering them to pure spread-damage-to-many sounds morely like another degrade to the new catalyzer mechanic.

4. Normal shots.

The normal shots are very good to move a close target fastly at distance. Of course, it could be nice if they had another shot or more range or whatever. But why do you want to change a weapon? Why don't you try to fit a place for it and check where you can use certain mechanics of a weapon and in which case you will use them? Yes, the Tortoguns are still the newest weapon types that got published amongst the weapons that are realistically obtainable, so you need to figure out where you can use it - and you definitelly can not use it on the same way as you can use a Brandish...

5. Agility.

There is a huge difference between old magnus mechanic and the tortogun recoil: You are instantly able to move around after releasing your charge - the magnus did knock you down on the floor leaving you vulnerable to everything.
Example: With the tortoguns I have no problem to release my crytals into the direction of a turret - even if said turret just shot bullets and one is directly heading to me. With the old magnus I could do the same but the rooting effect would cause you to get hit.

Tortoguns have zero rooting at all; they just push you back, which can often be used as great advantage once you got used to it.

I know where the charge bullets go... the problem is that where the bullets go isn't that effective against anything that moves faster than a zombie and relies on enemies walking into the impact zone for the most damage. I tend to pair my Tortofists with heavy swords so that if and when the charges do less than desirable damage I can still pin them up against the lodges crystals for solid sword damage.

The charge attack range is highly variable, sure it works at long range but you can just as easily walk right up to an enemy and launch a charge in it's face, the shards will always land near the enemies rather than right on top of them. When you are close however you can shield bump and sword push them into the impact.

Tortofists offer something unique in the game by providing a sort of wall that you can pass through but enemies can't. The Shards just don't last long enough to make a huge use of this. This weapon would be sooooo much more useful if it had the Shock status that the Real Tortodrone Shards had.

The normal shots are OK but have horrible range and a long reload time. They would also be much more useful if the bullet was shot along with the punch rather than after, that way it would feel more like a gun.

As for the agility I was referring to the regular attack and how it locks you into linear path while attacking when the amount of time between you clicking and actually shooting gives some enemies enough time to get out of the way. The Charge attack on the other hand has something unique to charge attacks in that it is the only weapon in the game to offer that amount of self pushback with no recoil. Useful for getting out of situations but it prevents your shield usage a bit since you have to have a charge ready.