Soul
Alright, let's settle this once and for all.
Asal damage cosists of two parts. The typical Magic Skill Damage, and the Asal-Specific part.
The regular skill damage is calculated like any other skill in the game and affected by Link Attack, PvP Sockets, and so on. You can get a rough idea how strong this part is by casting any other BP STR based still.
Note: This part isn't exactly as strong as the other STR skills. In eFlyff, since the damage is significantly lower than it is here, casting any other BP skill is a good indicator of this part of the damage. However, since the Attack% modifiers and STR is higher here, the difference in values become proportionally larger. The best way to calculate the exact Skill Damage part of Asal would be to subtract your Asal-Specific damage from your actual Asal damage.
The Asal-Specific part is what makes asal so strong. This is the part where the formula is most commonly discussed. This part is calculated using a formula with STR and MP being the only two relevant valueables, and it goes as following: (STR/10) * Asal_skill_level * (5 + mp/10). This brings us back to the formula Feedert posted. Instead of MP, it uses INT*2.25. This is because the Int per MP ratio for Force Masters in Mazey is set at 2.25 by default. However, this changes as your gear improves. If I'm not mistaken, the highest possible MP% modifier you can achive as a BP would be +3000%, which would result in 69.75 INT per MP.
In order to get your actual Asal damage, you simply add the Asal-specific part of the damage with the Magic Skill damage. Note that the Magic Skill Damage is going to differ as your STR changes though. If you calculate the Magic Skill damage at a certain Attack/STR ratio and change it signigicantly, you can cound with this ratio changing up to 10-15m~
Note that the final formula is going to give you the PvE Asal damage. This has to be multiplied by the PvP damage reduction in order to calculate your actual PvP damage. The PvP damage is set at 60% in flyff by default, which means you have to multiply your final value with 0.6.