So, I'm a bit conflicted about which specs to run with. I've been of the belief so far that Destruction/Demonology is the best combination, at least at lower gear levels. However, it's my understanding that at higher gear levels and with UVLS (Where I'm not, right now) Demo will go for Haste and Mastery, while Destro will generally mostly want Mastery, with backdraft + various haste procs (Heroism, Metagem, maybe Shado-Pan trinket, etc) swiftly making haste less useful. Affliction, again as I understand it, will want Haste and Mastery as well, similar to Demo.
This makes me think that gear-wise, once you get into some heroic gear, the best combination would be Affliction/Demonology. Destruction seems to outdo Aff/Demo mostly on Durumu. I had thought it'd shine on Horridon and Primordius (25H, all parses), but the difference between Destro and the next closest spec doesn't seem as massive as I first thought. 10k between Destro and Demo on Horridon, 15k between Destro and Affliction on Primordius.
So, it seems like in exchange for much more dual-spec compatible gear you give up the spec that is by far best for 1 fight, and in exchange retain top/contender positions on all other fights. Opinions/Facts/Wild Speculations? I'd appreciate any of it.