I think it could only be considered "OP" if it allowed a DPS to effectively solo. Which is sort of what we expect tower builds to be able to do in the first place. A better question would be, does it give an itemization advantage to DPS builds over Tower builds? IE, how many favorable stats does a Tower build look for and how easy are they to find on the same item, versus the same idea for the DPS character. If the elemental damage is an extra variable to optimal gear that the tower build doesn't have an equivalent variable to worry about, than it's going to be harder to find optimal DPS gear over Tower gear, and that seems like a strange disadvantage to have. A tower character can already effectively hold down multiple lanes simultaneously, (something very difficult to do as a DPS) so why should they also have the advantage of having 'easier' itemization? The question should be, are there comparable amounts advantages and disadvantages between Tower builds and DPS builds? How would making this itemization choice in favor of DPS builds effect that comparison?