for DPS, DNC is probably the easiest by a landslide.
after that, its arguable who is next. (A job like DRG is more simplistic in rotation than a RDM, but a RDM can pretty much just roll their face across the keyboard, and still do good damage, ignoring any possible complexity. Where as a DRG is severely punished for failure, even if it is simple, but RDM is not.)

Some jobs focus on multitasking more. Some focus on procs. Some focus on long rotations. and Some are more punishing than others (but not necessarily complex)
which of these were you looking for?
(DNC is still pretty simple, low end of punishing, and low multitasking. It does have procs. I personally hope they decrease its GCD for the next expansion. Theres no reason it cant have a 2s GCD with how simple the job is.)