4th job Single Target DPS

Uh... one formula I've seen that works reasonably:
Charge #1: calculate normally
Charge #2 (always Lightning when 2 charges are present): divide by 10 the result
Add the 2 to get output total.

Eg. Holy (weak) + Lightning (neutral) 150% + 125%/10 = 162.5%
Holy (weak) + Lightning (neutral) 150%*150% + 125%/10 = 237.5%

I don't know if this is right but it's way more accurate than multiplying the 2.

Someone also suggested that the second charge is stacked on after multiplying by skill % but I can't confirm that either (thus making Lightning add less damage to Blast?)