Damage Calculation

Anyone knows the Damage calculation for skills?

The one that's in the helper doesn't seem to make any sense.

Here's what i figured out so far, out of many tests:

I know that 2 def = 1 att, and the exact damage calculation if theres no def which is:

ER = Effect Rating
FD = Final Damage
AS = Attack Stat
AI = Att Influence
II = Intelligence Influence
VAR = Variance
DMG = Damage


-AS = Att of the character(or ennemy)
-ER = Effect Rating. Direct Skill Damage. 1ER = 1DMG.2000ER = 2000DMG
-1 AI = 5%  If boosted at 10 = 50% .Same for II.
-VAR = ± 5% range att

Round every numbers.
       
Example:

ER: 215
AS: 75
AI: 3
Var: 5

(ER)+(AS + AI%) = VAR25% FD
  215 + (75 + 15%) =  X
  215 + 11 = 226
    226 - 25% = 169.5
    226 + 25% = 282.5
      FD: 169~282


BUT whenever I apply Defense, even if i do ½ stuff etc, it fucks it up. on top of that, Att influence fucks it up even more.

So, help anyone?

Thanks.