Note everything is taken from the JP wiki[www62.atwiki.jp]. I have physically calculated all these myself using the formulas provided. So the formulas provided are more or less in the ball park.
There's a bit of math involved in this post. If that doesn't interest you just read the first section for elemental damage to help you get a little more damage for casually playing.
I might add Blood Arts some time later if there are people actually playing the game still.
If I get the time to it I'll create another guide with aragami defense ratings.

In summary, if you want to get a bit more damage out of your sword, craft one for each element and bring the right one for each mission. On the other hand. For guns it's highly recommened to NOT get one with an elemental multiplier because the uses are limited and the Crush/Piercing values are dramatically lowered. The elements attached to the bullets themselves in the bullet creator is more then enough.
And in the case of Reinforced weapons, the game will only use one element for it's attack, and it's not RNG based so it's forgiving. So if you hit a spot that's weak to Blaze, Spark, and Divine, the game will make your attack a Blaze or Spark element but not Frost.

(Base Weapon Power + Adding Correction) × Multiplication Correction × Elemental Multiplier × [(100 - Aragami Defense) ÷ 100]

Note, weapon pluses (upgrades) are included in the Weapon base. HOWEVER, the game will automatically apply the 20% from the skill "Melee ATK" into the status screen. Upgrades for swords grant a +.01% in base damage capping out at 1.3.

Note, you will almost never get a "Hidden Attack" unless you're using the sniper's steath field, but this is the wrong guide. Or you have the skills "Muted" and "B Super Muted" and the aragami doesn't have you in their line of sight. Also blame your teammates cause if they disrupt the aragami before you attack, then you won't get the Hidden Attack Buff.

Rising Edge: R + □ buttons to use.
Advanced step / jump: ○ or × button to use (Can only be performed at in the middle of a combo).
Aerial step: ○ button to use (Must be in the air) Consumes stamina like normal.



Because of the way the skill "Combo Master" works, Short Blade is the best weapon to use with it.

Zero Stance: R + □ buttons to use. Regain 10 ST. Also an animation cancel.
Impulse Edge: R + □ buttons to use (Must be in Zero Stance). OP consumption varies, (40, Bursts Lv1 32, Lv2 24, Lv3 12) affected by the skill "Trigger Happy". The action is extremely loud and will cancel the skill "Muted".

Charge Crush: hold □ button to use. Movement and action is restricted, you can still aim. ST decreases for as long as you hold it. The action is extremely loud and will cancel the skill "Muted".
Advanced Guard: After any ground action, you can guard at a set rate. Unaffected by the skill "Guard Speed" or shield types.
Parrying Upper: R + □ buttons to use. Guard for a moment, followed by a counter attack. Consumes 20 ST. Negates all damage if successful. Not recommened for multistage attacks.

No one actually uses this. But I'll include it anyways.

Boost Ignition: R + □ buttons to use. The action is extremely loud and will cancel the skill "Muted".
Boost Rush: □ button to use (Must use Boost Ignition before). Consumes 10 ST.
Boost Drive: △ button to use (Must use Boost Ignition before). Consumes 10 ST.
Boost Impact: R + □ buttons to use (Must use Boost Ignition before). Consumes 25 ST. The action is extremely loud and will cancel the skill "Muted".

Charge Glide: Hold □ button. Dash foward on release. Consumes 10 ST. Movement is not restricted. "Auto Guard" skill will still block. Damage increases by 20% during deployment state. It will return to normal after the final Auto Attack Chain, Getting hit, or Blocking.
Backflip: R + □ buttons to use. Will put you in the sky, and can dodge some attacks. Consumes 5 ST. It's possible to hold Charge Glide "Charge" by using backflip.

My personal favorite weapon choice.

□ Attacks are short ranged.
△ Attacks are 2 medium ranged attacks.

Round Fang: R + □ buttons to trigger. Scythe enters deployed state. Consumes 20 ST. Two cleaves strating from the left followed by a one starting on the right. Enables Multihits. Hits about 180 degrees. After stepping, you can maintain deployed state for a while. The most damage comes from the tip or edge of the blade.
Vertical Fang: △ button to trigger (Scythe must be deployed). Scythe drops down exteneded. Consumes 10 ST. Likewise the most damage comes from the tip or edge of the blade.
Cleave Fang: R + □ buttons to trigger (Can only be used after Vertical Fang). Scythe retracts, slicing everything in between. Consumes 15 ST. The most damage comes from the MIDDLE of the blade

So some people I talk to have noticed that there's a skill called [Sunburst]. It grants an amazing -10 to the attack speed stat. While I only played with Scythes enough to have a melee attack skill up, it should be more or less in the same ball park. Hammers and Busters maybe have a greater effect, but I can't test that out.

I would make a video running each attack speed side by side, but I don't believe I have the technology to do so. So for now screenshots are the next best thing.

The one on the Left has sunbusrt
The one on the Right has Melee Attack Speed (positive)
The bottom one is normal speed.
This is 10 frames after I aligned each video capture.
As you can see there's a kind of a difference already from the start. They seem to just be each 1 frame apart from each other.

This is 10 frames after the first picture, or 20 frames after I aligned each video capture.
The difference between the sunburst and normal is pretty notable, yet the melee attack speed up isn't changing by much.

This is 10 frames after the second picture, or 30 frames after I aligned each video capture.
Nothing new here, it just reinforces the previous images.

This is 40 frames after I aligned each video capture.
Now here's the interesting part, I checked it again but notice how the normal speed and melee attack speed are around the same time now? Melee attack speed is still faster but it's only by a tiny nudge, probably not noticable with normal gameplay.

I'm not telling you that [Sunburst] is a bad skill. I'm only showing the negative qualities. But the reason why I used the fang deployment and not a regular auto attack is because I wanted to show that melee attack speed not only affects auto attacks but also special actions. But why does that matter you wonder?
I have an insane friend on steam who uses nothing but the Blood Art Final Vengence. Now one night he wanted to test out the skill [Sunburst] and needless to say it ended poorly. This is because melee attack speed also affect the parry window on Buster or Execution Blood Art on Scythes (but I didn't test it since I'm not a fan of that BA). So in some cases this skill might be helpful if you want to slow your attacks, but I can't think of any Blood Arts I currently use that would benefit from it.
Now the skill itself. While it has other amazing components, you need to ask yourself is it worth the -10% attack speed. Don't let this little section discourage you from using it. Play the game how you like. I'm just here to let you know if you feel like your timing is off and you have the skill, it's probably why.

Now for Melee attack speed up. There's not much to say about this skill. The only question you need to ask is, "Is the small frame differences worth a single skill slot?" As there is no skill in game that has melee attack speed up. If you want my personal opinion, notice why I'm using the basic kurogane colors? Yeah, I don't recommend this skill 'specially when Evoke Rate or Blood Rage Duration is much better. But that's just my opinion.