So after gathering all the damage numbers for Guild Training Hall, I noticed a lot of weapons shared damage.

-There are the obvious things, like Gran Faust and Divine Avenger being identical in damage values. Other obvious ones are Flamberge/Rigadoon, Flourish/Thorn Blade, Triglav/Suda, Pepperbox/Plague, all the status alchemers, all the brandishes, Umbra/Nova, all the haze bombs, Iron Slug/Callahan, DBB/Nitro, the four pure damage shards bomb, the two specialty shard bombs, and Hunting Blade/Venom Striker.
-Valiance' regular shots match up with non-ghost strikes of Wild Hunting Blade.
-Dark Retribution matches with Plague Needle's regular shots.
-Hammer's dash matches up with Furious Flamberge's first strike.
-Hammer's other attributes match up with Sudaruska.
-Biohazard's charge matches up with Callahan's charge.
-Neutralizer's charge doesn't, and has a unique value!
-Polaris unexpanded shots match up with status alchemers and Catalyzer. Expanded shots match up with nonstatus alchemers. The charge matches up with Nova/Umbra's charge as well.
-Supernova's expanded shots match up with Iron Slug. Other values are like Polaris.

And maybe some others I forgot. So which weapons should be tested in order to do the fewest amount of tests and still get a complete picture?

Swords
-Final Flourish' finisher has unique damage, and as such tests are required. All the other damage values are identical to Leviathan Blade, and as such Levi requires no tests. The charge finisher on Flourish also corresponds to the charge attack with Suda, making Sudaruska entirely redundant.
-Barbarous Thorn Blade has unique damage values on the spikes. The charge stroke is otherwise identical in damage to the first two hits in Flourish' charge attack.
-Flamberge has some unique values.
-Cold Iron Vanquisher has unique values for the combo, so those need to be tested. The charge can be covered with Flamberge's finisher, and as such only the combo is needed.
-Warmaster Rocket Hammer is somewhat needed as you can't get "weak" and "resistant" values on Sudaruska. Otherwise it would be obsolete. One needs to gather the final stroke and the charge stroke.
-Fang of Vog has all unique values. I suspect there are split-damage shenanigans going on, and that making it pure damage would line it up with something or other. Until we can figure out an exact formula on how that works, FoV needs testing.
-Pick a brandish. Any brandish.
-Divine Avenger is preferred to Faust, simply because charging it is faster and as such the numbers are easier to gather.

Flourish, Thorn Blade, Flamberge/Rigadoon, Cold Iron, Rocket Hammer, Fang, Combuster, Divine.

That's 8 swords to tests to find the values of about 20 swords. Swords are the worst in this aspect, frankly, not the least because they have so many aspects to test.

Handguns
-Status alchemers have unique damage on the charge.
-Neutralizer has unique damage on the charge, and as such needs testing. The regular shots are covered by status alchemers.
-You can either go with Polaris or a nonstatus Alchemer. The charge and shot damage is shared between them. Having one makes the other obsolete.
-Callahan's shot damage is identical to Supernova's expanded shots. However, since Callahan is specialised, you can gather more info with it. Callahan's charge damage also covers Biohazard's. The regular shots cover the charge strikes of Wild Hunting Blade.
-Bltiz Needle, Argent Peacemaker and Sentenza all share both damage values. It doesn't matter which one you pick, but Blitz' numbers may be easier to gather on the charge than the other two. The regular shots cover the ghost strikes of Wild Hunting Blade.
-Plague Needle can be used to cover the values for both Pepperbox and DR. This does not work conversly, and as such you'll specifically need Plague Needle. Sorry, you'll have no choice but to Lockdown a bunch for science.
-Valiance has unique damage on the charge. You can use the shots to cover regular swings of Wild Hunting Blade.

Hail Driver, Neutralizer, Nova Driver, Callahan, Blitz Needle, Plague Needle and Valiance.

7 guns to find the values for 17 handguns, 1 sword and 1 bomb. That's a little better than swords. It's also far less shenanigans going on with different charge damages and combo damages.

Bombs
-Dark Briar Barrage has specialised damage where Nitro does not.
-Dark Retribution is not needed, as the damage can be found using Plage Needle.
-A haze bomb or Electron Vortex. It matters not which.
-Graviton Bomb has unique values.
-One of the Deadly shard bombs except for actual Deadly Shard Bomb, as you'll want to find special damage values.
-One of Scintillating Sun Shards or Shocking Salt Bomb. It's irrelevant which. The core won't be needed as that one is shared between all shard bombs.
-Irontech Destroyer has unique damage values.
-Big Angry Bomb has unique damage values.

Dark Briar Barrage, Ash of Agni, Graviton Bomb, Deadly Crystal Bomb, Scintillating Sun Shards, Irontech Destroyer, Big Angry Bomb.

7 bombs to find the values of 17 bombs. (There are 18, but one was found using Plague Needle.) About the same as guns, in that regard.

So there you go, 22 weapons to test out over 50. Doesn't seem so bad now, does it?