So i'd like to just say that I only own the Grand Tortofist personally, but have spoken with other knights in lobbies while running through the depths, and most of them in the past have agreed that they should be better.
This being said, it'd be hard to make them flat out "better" without simply amplifying the damage values straight out, which there is already a forum post for which I'll link here:
http://forums.spiralknights.com/en/node/118737

This being said, I still have an idea for this that doesn't involve a flat out buff of damage or change in rng, as well as some other suggestions in the offchance that people hate this entirely.

Okay, first of, I'd like to just put my two cents into this matter before I get into the suggestion upright, so if you don't care for that please skip this paragraph. The main reason I feel that the Tortofist line deserves a change to become more useful is due to the level of difficulty to obtain it. Once you do finally spend hours of grinding to get glyphs, or spend thousands of crowns to buy them, you're then met with the struggle of finding a good group to fight the Tortodrones with. Now, even if we assume that you're well off as a Knight and have plenty of very skilled friends, the boss fight is still challenging, and it's amplified further when you throw in the seemingly constant lag spike issues that seem to affect random knights and wind up costing them sparks. In the end, to get my Grand Tortofist I probably spent somewhere between 10-20 sparks, thousands of crowns (let's say around 30k because turtle shell drops hate me), and then I had to spend the normal amount of money to craft the line itself. Now, in my mind I hoped that the 5* would be fun as hell to use. It's one of the only weapons on the game that works the way it does, and it's based off the Tortodrone's attacks! I personally expected the basic hits to be knockback-central, and for the barrage of rock missles as a charge to deal severe damage. And....what I got instead was a feeling that I had wasted hours of my life for what very well might be one of the weakest and most impractical weapons in the game. It was made even more shameful when it hit me that the biggest reason those spikes even hurt me during the Tortodrone fight was due to the difficulty of dodging Devlites, spikes, and often another Tortodrone lunging at me. When it comes to simply launching some spikes as a sort of mortar-fire- and nothing else- it just isn't useful. Not only that, but when a sword user comes up and starts killing everything and knocking them away it just makes the weapon entirely useless to bring. The sentence "Well if it's that shitty sell it, or just don't use it" keeps coming to mind; but the thing is I solidly believe that even if it requires specific use to be good, like teaming up with a friend, a weapon should be usable without killing myself. For instance; the faust is good if you can play with a slow sword, the Fang of Vog can be safe and still devistating to use if you have fire resistance, etc. The tortofist's only real meta here seems to be "GET FOUR PEOPLE WITH ASI:MAX AND CTR: MAX AND SPAM IT". That's....horrible. That being said, here's what i'd like to suggest!:

Suggestion 1: Status Effects
The first thing I noticed about the Tortofist line is the lack of status affects. When facing the boss he fires purely Piercing damage spikes that inflict stun damage. When you the player recreate the Piercing tortofist, you fire purely Piercing damage that inflict nothing. Well to me this brings up two possible ideas; the first is to simply add in a slight stun chance for the shot-part of your basic attacks, and to throw in a strong chance of stunning enemies with the charge attack from each barrage. I feel like this could be very useful in Arena levels- or really just any button area that has you facing a mob of enemies. This would make the weapon feel more usable as well since I'd feel safer lunging myself into enemies knowing that they'll possibly be stunned, and I wouldn't feel like i'm crippling my group if I knew my weapon served a useful purpose like stunning the enemies that it hits/that run into them when I shoot off a charge attack.
The second idea I had about this was to piggie back off of the Shields and give them the relative statuses. Basically, the Grand Tortofist would only do stun, like how the shield prevents it, however the Gorgofist would deal Freeze and stun, The Savage Tortofist would do Poison and Stun, and the Omegaward would do Fire and Stun.

Suggestion 2: Knockback for basic hits
I understand that the weapon already has some slightly knockback, but it doesn't effect larger enemies and it barely does much in my testing of it to even smaller enemies. I feel like it'd be more helpful for the basic hits if the shot part of them had an increased knockback, not quite as wide as a faust line sword, but similar in terms of knockback distance. I'm not saying we should be blowing enemies away, but at the same time when we faced the Tortodrones they threw us around the map. I know that the shields sort of do this with the shield bash effect, but I feel like some of that knockback power should still be present in the hits.

Suggestion 3: Damage increases
Like I said in the begining, someone has already talked about buffing the damage, but to put my two cents into it: While some think that the damage is workable, I disagree. I'll admit mine is only a level 4 Grand Tortofist, but at 5* I'd hope that it'd be stronger then most 4* weapons. Without damage bonuses it's doing 44 and 59 damage, twice, for the entire hit. That's just literally 103 damage for the first two hits, 206 in total. The weapon also lunges you into enemies to do these strikes, of which if you count the lunge/bullet together it only hits twice. Meanwhile, the Valiance does slightly more damage, is easier to use as a gun, is insanely easier to craft, and is much easier to use. The charge hit of the Tortofist isn't much better, each shard hits for 83 damage and then ticks 3 times at 55 damage. The ticks, dispite there being what I believe to be an update stopping Invisiticks, still effect my gun for some reason. Mix that with the fact that the 83 damage can only hit up to three times through my practice, the charge hit at level 4 has a maximum damage of 83x3 + 55x3, or 414 damage. I can imagine that this number, by level ten, would go up to around 500 if mixed with damage bonuses, but that's still not very high. To put it plainly, this weapon is out-damaged by virtually every 5* weapon I can think of, and even the ones that don't flat out do more damage (like a node slime crusher, for instance), can be used more effectively since they operate the same way as a faust, and run less of a health risk in the long run. To finish this up, i'd simply say boost the damage all around by an amount that makes it worth the horrible grind but not terribly overpowered. It shouldn't be that hard, something relatively small would probably work, but at it's current damage rates it's pretty hard to ever justify bringing it anywhere.

Okay so that's basically it in a nutshell. I'd like to see some Status effects, knockback with the basic hits, and maybe a bit more damage to help round the line out and make them more fun to use.
Okay, insults and criticism time, go. do your thing!