Mages are always very new player friendly, easy to understand, easy rotation, but if mage does not interest you or you find it too easy you could try demology warlock. Demology warlock has easy rotation, but a lot of abilities so you might need to use macros or it can feel overwhelming.
Demo warlock in simplified nutshell : keep your pet on target, you refresh your dots and spam shadow bolt and incinerate when you have proc for it, use demon form for additional burst damage when wanted, when target is low health you move to your execute phase and start using soul fire.
Ele shaman and non-fire mages are both a good pick for a slow ranged class.
I’m not sure how good you are managing DoT’s because then you could be Affli. I’d rather not pick Shadow however, it’s not easy to learn and its aoe is clunky as hell currently.
Not sure on the upcoming Evoker as I didn’t get the beta.
Boomy gets complicated when you try to min-max it, and if you don’t bother, your DPS can suffer a lot. You need to watch eclipse timers, hold on to resources for the correct burst opportunities, manage multiple DoTs, etc. And their hard-casts make them somewhat immobile while DPSing. There’s quite a lot you can do wrong as a Boomy.
Elemental has, AFAIK, has some builds that are super easy, but also some that are super hard (Icefury?).