The reason people view affliction as "hard" to play is that it's just different, especially in comparison to Vanilla and Burning Crusade days. Vanilla consisted of SM/Ruin as the "raiding" spec, while Burning Crusade was essentially a shadowbolt spam. Honestly, I'm very disappointed that the affliction simplication is actually happening. I was really enjoying the unique playstyle.
Currently, Blizzard does need to have some way in their default UI for you to track your OWN debuffs. Almost every class can agree to this - the default UI is simply ineffective for tracking anything related to debuffs or DoT's.
I really think the way to get someone who was "bad" at an affliction warlock playstyle and wanted to get "good" is to put physical cooldowns on the DoT's. What if when you cast corruption, you couldn't cast it again for another 18 seconds? Or what if when you cast UA, you couldn't cast it again for another 17 seconds? Suddenly our priority system would become no more complicated than an enhancement shaman or hunter.
--> Hit the buttons the moment they come off cooldown, and if there's ever a conflict, just check the priority.
That's basically what several classes do. Shadow Priests, Hunters, Enhancement Shamans, Elemental Shamans, etc.
So many people lose DPS because they can't translate DoT's to a cooldown. They can't get the priority system right.
WARNING! MSPaint incoming!

I honestly think the ultimate warlock affliction mod, for it's current state, would display 5 debuff icons: Corruption, UA/Immolate (one icon), Curse of Agony, Siphon Life, and Haunt, and have them be in that order, as marked above. Each one would have a timer on it until the next time you need to cast that spell. For the instant spells (Corruption, CoA, SL), the timer would be exactly equal to it's duration. For UA/Immolate, the timer would be 16.8ish seconds (assuming 1.2 second cast time). With a 1.5 second cast time, the timer would be 16.5. You get the idea.
Each one displays a fake "cooldown" time on it. Whenever there's a conflict (2 spells coming up at the same time), you just pick the higher one first. When the timer is 0, have it blink at you or something. This idea would essentially translate DoT timers into "cooldown" timers, which are much easier for people to manage. Having the hierarchy there and directly in front of you also helps a lot - I know I organize my main action bar from most to least important, and I do think it helps a lot (while now I have my priorities memorized)
Anyways, you get the idea. The problem with affliction now is that some people don't have the mental capacity to translate DoT timers into cooldowns on the spell, which makes DPS'ing with it impossible. Imagine a bell curve of DPS. For affliction, it's very steep sloping - clipping DoT's has a BIG impact, while not keeping DoT's up has a BIG impact. For 41/30, not so much.