Warlocks at the moment are all about generating resources and then spending them on high-damage abilities. The clever thing about the system is that it allows you to save your high-damage phase for when you need it, with a fair amount of wiggle room for doing so without losing any efficiency. So you can save it for a burst phase, or just hit it when your trinkets proc.
As mentioned before I quite like the way Destruction feels for single target fights. The mechanics are simple enough; generate Embers, aim to have close to four when Dark Soul comes off CD [or save for the burst phase] so you can get three to four Chaos Bolts in while that buff is up, otherwise spend Embers during your most powerful trinket proc.
Still getting a feel for Demonology. Switching in and out of Metamorphosis at will is a really cool mechanic with multiple uses. I really would like to see some better theorycrafting for Demo. Or I suppose I can just go do a bunch of dummy testing. What’s harder to test, though is the value of Demonic Fury generation. Currently I only cast Doom and Touch of Chaos while in demon form, because I my understanding is that Soul Fire is more valuable as a Fury generator.
Speaking of theorycrafting, wtf is the deal with Noxxic. Those guys seem to just make assumptions based on the tooltips and present them as fact. I lost count of the number of times while reading their pages on both Warlocks and Warriors that they basically just rephrased the ability tooltip and followed it up with the most useless advice like “use this when you need AoE damage”.