Perhaps you have observed that every offensive skill has the following form: DAMAGE followed by a PROCENTAGE.
e.g. Flame wave arrow lv.1: 123~205 (250%). Heaven lion shout lv.1: 126~233 (100%). Everybody can observe that at a specific level (for example 40) the flame wave will do way more damage then the shout. The damage ranges being roughly equal, the conclusion can be drawn, that actual damage has something to do with that procentage. Nothing new so far. I think the procentage after the damage has something to do with the skill’s casting time. Another example: after precise measurements I have determined that the casting time of Strong Bow is precisely 3,5 seconds. The damage of Strong Bow Spirit lv.1 is: 70~95 (350%).
Let’s have a look on Anti Devil Bow – Wave lv.3: the casting time is exactly 2 seconds; damage: 70~95 (200%). So the procentage is consistent with the casting time, but Strong Bow deals more damage then Anti Devil Bow, roughly 1,5 times more. Damages also have to do with parry ratios and I haven’t fount any formula for damage yet, but theoretically, the damage of the skill should be enhanced with the procentage to produce the actual damage. In general: CASTING TIME * 100 = PROCENTAGE AFTER DAMAGE. This applies to all offensive skills. As a conclusion: the longer a skill takes time to execute, the more damage it deals. In addition to that, if you imbue your weapon, the imbue will take effect precisely one second after pressing the key. This is also consistent with the numbers (Extreme Fire Force lv.1: 62~103 (100%) )
There is one more thing that needs to be settled: combos. Soul Spear Soul lv.1 has the following figures: 275~353 (175%). Multiply the procentage by the number of successive shots/hits, divide by 100 and you obtain the casting time of the skill (in this case: 3,5 seconds – it has been verified). Billow chain (5-hit) lv.1: 71~86 (68%). Casting time: (68*5)/100 = 3,4 seconds: measured and proven. If you can come up with a counter-example, please write so I can modify. Hope it helps.
NOTE: don't be too hard at me if i've said something wrong; i'm just a maths freak who's done some easy calculations and measurements.