I really love using my omega tortofist on FSC and Savage Tortofist on fiend runs but tbh they are very gimmicky especially the pierce and normal variant.
Omega Tortofist somehow works well on FSC, atleast better than elemental alchemers when dealing with swarms of slags... but its non-party friendly to both your teammates and the user itself.
The tortofist's charge attack is somehow "nice" and its potential overall dmg/charge attack is comparable to blitz but getting the highest potential dps is almost impossible unless you managed to land the shards before the vortex spawns. (vortex bomb of other party member)

Here are the cons of tortofist:

1.) Its charge attack's knockback can ruin kitings as it would push some slags on random direction like a small blast bomb.
2.) Its normal attack dps is even weaker than Arcana/AP shots, I'm aware that its normal attack is used to push the monsters to the shards to deal more dmg but its hard to do it because of the shard's knockback and the risk of getting scratched in the face.
3.) Shards takes time to land.
4.) Shards' AoE circle doesn't capture targets sometimes. (most notable when you targeted a group of slags clumped together).
5.) Some shards doesn't spawn when there's no more unoccupied space for them to land.
6.) Can cause some lags.

Here are my set of suggestions for buffs:

1.) Add SHOCK status chance (high) to all tortofist guns... why not? tortodrone's shard cannon can shock ppls so why not the tortofist guns? It will also prevent targets from getting knocked back.
2.) Add more dmg to normal attack. (atleast 300-350 dmg on bonus monster-type dmg)
3.) All shards will spawn a mini vortex that would pull monsters
4.) Shards should land faster.
5.) Normal-Type Tortofist should have a slightly higher base dmg than other tortofists.
6.) If not suggestion 1 or 3, atleast remove/reduce the knockback of the shards.

Other Suggestions:

Handguns:
To be honest, elemental handguns (taking aside mixmaster) that are meant for dps (Nova/Magma/omega torto) are underpowered on PvE party runs in my opinion, that even a properly-used iron slug would easily beat those. Umbra Driver, Wintergrave, Repeater, and even Phantamos does their job well done against shadow-weak targets on parties without being outclassed/outDPSed by other party members.

1.) Slightly more dmg to alchemers, atleast make the status variants have the same dmg with the pure dmg variants, and atleast +40 for max dmg on pure dmg alchemers.
Alchemer's internal richochets' DPS being OP and Nova Driver's charge attack claimed by some ppls that it can 1-shot kill a slag on a fully party run... are overhyped imo.
2.) Just like Acheron -> Obsidian edge, Shadow Alchemer needs a poison status variant.
3.) Magnus' charge attack knockback needs some fix.
4.) Antigua lines needs slightly more dmg, sentenza's gremlin bonus dmg is almost useless.
5.) Autogun lines' charge attack sometimes doesn't spawn bullets when shot directly to the target, most notable for me is when you shot a charge attack on toxoils directly.
6.) Catalyzers needs some rework.
7.) Pulsars... Jesus Christ... I hate seeing them on both PvE party runs and PVP. Idk what to suggest on this gun.

Pulsars are disgustingly overrated. Labelled as a powerhouse of dmg???. You'll mostly see them being used by newbies and noobs as their main DPSers on public runs. Shooting 3 shots straight on targets until they get pushed to the corner. Most of them aren't aware that they are killing overall party DPS and putting other party members on risk of getting hit.

Swords:
Tbh for me, there are only 4 sword lines in SK: Brandishes, Sealed Sword, Flourish, and OTHER SWORDS.

1.) Troika and Calibur lines should have shadow/elemental dmg variants.
2.) I think the charge attack of DA and GF needs some fix.
3.) Spur line needs a 5* upgrade (shadow and elemental)
4.) Amputator is almost useless, maybe atleast add a STUN status chance and slightly more dmg.
5.) Cutter...Idk how to fix Cutter lines, some ppls said that its one of the best swords if you know how to use it but for me, they are still gimmicky even though they can still do their job. More effort but less rewarding. I think adding elemental/shadow variants might be good enough.
6.) WMRH's charge attack, I know its not a charge-oriented sword but atleast make it a little more useful and less non-party friendly.
7.) Calibur's charge attack should have less knockback.