I wouldn't mind it having a slight damage increase and decrease based on the element of an attack, though your proposed method will certainly go over far better with the community who are either constantly begging for changes to the classes that aren't over powered or are constantly complaining that the other classes are too over powered, despite there being a clear balance between them all. Still, in the vein of complaining, I have always found it pointless to have the elemental types to begin with if they have no bearing on combat in any way. Especially since they also saw fit to include that the Arcanist attacks are "unaspected" meaning that they would remain equally effective or ineffective against all enemies. As it is, this serves as nothing more than flavor text, (don't get me wrong, I love delicious flavor text), which begs the question of why include it to begin with?