Is this normal? heh
 

Harm being a level 1 spell (i.e, buff = 1)

If

• Your chara has lots of MAtk
• Thunder Flan has low MDef

then yes.
Buff is just what the weapon adds to your existing stats, which, combined with your element, is matched towards the combined stats and element (IE if your element would add extra damage, or halve it. Strengths and weaknesses in the ACP is what Im referring to) of your opponent. It is not an indicator of exactly how much damage will be done. Potions is the exception as the buff represents the actual value of healing.
And theres also the fact that most things has the +/- 10% variable, to have it abit more random yet not fluctuating from 0-max like a certain other script *cough*