According to Doctor Manhattan, none of the magicians in the DC universe actually use magic. One of the most powerful characters in comics history displays his full power in Doomsday Clock, a limited series written by Geoff Johns with art by Gary Frank and colors by Brad Anderson. The series bridges the gap between the DC universe and the world of Watchmen, the landmark work by Alan Moore and Dave Gibbons; Doctor Manhattan originates from Watchmen, and with his nigh-omnipotence, reveals the secrets of magic - through science.
The failure of the New 52 prompted DC editorial to reboot their universe once again with the DC Rebirth initiative. This in turn led into Doomsday Clock, a convergence of the DC and Watchmen universes in which Batman encounters Rorschach, Lex Luthor meets Ozymandias and the entire story seems to boil down to a showdown between Superman and Doctor Manhattan. Manhattan, who perceives time in a non-linear fashion, is unable to see past this meeting, leading him to assume only two terrifying outcomes: either Superman destroys him...or he destroys everything.
In Doomsday Clock #9, Doctor Manhattan defends himself against an attack from dozens of superheroes, including the magic-based members of the Justice League Dark. After Green Lantern's attack fails miserably (Manhattan even dissects his ring), Zatanna and Constantine attempt to burn and freeze Manhattan. "You all believe you're wielding magic," Manhattan muses as the League's attacks serve as little more than an annoyance. He further observes that the team is harnessing the "scraps of creation", similar to errors in computer code, which are quickly tossed out by programmers. "Left to be picked up and used by those who also find themselves discarded and forgotten." Manhattan's observations that "magic" is merely leftovers from the creation of the universe is appropriately chilling; not even the most powerful sorcerers in the DC universe can hurt him.
Doctor Manhattan is analytical in every situation, but it's especially noticeable when he can't see the future. Before he became the most powerful being in the Watchmen universe (indeed, the only superhero who actually has powers), Jon Osterman was a scientist, after all; magic in the DC universe would certainly be a new sight for him. While the Marvel universe has multiple scientific explanations for sorcery, magic in the DC universe isn't meant to be understood, merely to be used to see the (often horrible) truths about the world.
Doomsday Clock proves that Doctor Manhattan is so far removed from the ordinary world that he can perceive what others cannot - even powerful magic users. For Manhattan, there exists a scientific explanation for everything. The downside of his phenomenal powers in Watchmen is his gradual disconnect with human emotion...but this quality (or lack thereof) is what makes Doctor Manhattan the perfect scientist.