I've found Demo to be far better than Destro, and be much better at surviving as well. Sac Pact Demo with a Wrathguard with Demon Training glyph gives you a 300k shield every minute. Combine that with double port, Axe Toss, knock, and leap, and you're pretty strong at surviving.
The damage seems pitiful when you play it, because so much of it is in pets and Doom/Corruption, spread out over huge periods of time. But the damage is kinda there, and the burst when popping your Dark Soul is still reasonable. Although I usually just play around keeping Doom up, more than actually doing the Dark Soul 2x Chaos Wave against most teams that don't have 2 curse dispels.
The more I try Aff the more I'm convinced that the #1 problem by a significant margin is the survivability, particularly against cleaves. It's just fucking awful.
Hm i think it has a lot to do with the setup i've been playing, shadowplay. It's extremely hard for me to die in this setup due to my cd's/self heals which forces most cleaves to sit on our shadowpriest/shaman and if i'm honest you can't outheal a destro that can free cast, some of our games have been moderately long but others we just win because i can get a chaos bolt off when they are 50% which is almost a garanteed kill.
I don't need a 300k shield playing this setup, i just need the immune to damage for the occasion where maybe the kfc/kitty does decide to burst me down(and a 300k shield here would last maybe 2 seconds lol). Outside of that i can last almost anything with self heals+spriest support. The double port would be pretty nice although i'm not sure how much it will really come into play in this setup.
The main thing i think gives destro the edge is the burst damage, if i cast 2 incinerates that crit with a conflag that person is dropping to 50% or so with my spriest dots on them, it's very easy to land some kind of cc on the healer and we can shadowfury the person, if the person does not trinket they die 100% every time, we are 30-2 at the moment with 1 loss being from leaving the queue as it popped, i felt near immortal when we played and the controlled burst is very high.
Affliction has good damage but yeah, you cannot survive as it, everything warlocks previously had in terms of survivability has been removed and we now have basically 2 defensive cd's that are useful as affliction, and the absorb shield isn't even that useful because it's gone in a mortal strike anyway.