One of the mistakes I often see people reading the 3.1 patch notes is they often read the change to the tooltip and they think that's all they need to know.
Many probably read "Molten core has been moved to tier 6 of demo" and thought "Well, that's good for demo I guess." But is it really good for demo? To fully understand patch changes you have to know where all the talents are relative to one another. I'm here to tell you that maybe it's bad for both destruction and demo.
I'll start with what I think of affliction changes.
The most controversial change warlocks got this patch was the removal of siphon life as a spell. Considering siphon life did about 11,000 damage for one GCD, this a pretty big hit to affliction's dps, around 8% (that's a lot for one change people). Many argue that this is fine because it's "More time to shadowbolt now" which to me is kind of silly. First, siphon life only had to be reapplied once every 30 seconds which wasn't asking much. Second, we're talking about an instant cast that does 11,000 damage vs. a 2.5 second cast that does 3-4k on average. That's hardly comparable.
Suppression is now a 3% chance to hit bonus for ALL spells. No more need to pick up both suppression and cataclysm but this does actually hurt FG/emberstorm which can't afford to put points into affliction.
Affliction's damage will also go down a little due to changes to eradication (no longer a haste buff) and shadow embrace (no longer effects direct shadow damage as well haunt (no longer effect fire damage dots like immolate). Though not a change to affliction the move of molten core no longer allows affliction locks to get it either so immolate will take huge a hit to its damage overall. Still worth keeping in the rotation, just not very impressive for a dot anymore.
Pandemic is now 1 talent spend for the ability to make corruption and UA crit. This is a little different from the old pandemic because now the crit bonus damage is 50% compared to 100%. While this makes the single talent spend a better budget, the talent is less potent overall and much less preferable for pvp now.
Now demonology
Fel synergy's move to the first tier but loss of the stat increases may read as a nerf but its actually good news for levelling and pvp'ing affliction/destruction locks to be able to pick up the talent in the first tier.
Demonic sacrifice has been been removed and mana feed truncated to 1 talent point in its place. I think this is a good though mostly unnoticable change. Long gone are the days of 0/21/40, DS really had no place.
Now molten core is the most elusive change. Considering demo locks already put at least 15 points into destruction this really accomplishes nothing at all but hurt destruction. Most interestingly, it also only allows FG/emberstorm to get 1 point of molten core if you want the more important talents. Demo's own best spec actually hurts from the molten core move to demo, kind of ironic eh?
Though additions of nemesis and decimation look good for demo, I don't see specs past 41 into demo as being able to compete with the damage boost of mutually exclusive emberstorm.
Destruction
Improved shadowbolt now simply increases the damage of SB by 5% and gives an inferior improved scorch (thanks lillia), 5% crit. This gives affliction some utility, otherwise, not a very noticable change.
Destruction's dps made some tradeoffs. Improved immolate and conflag on the way up, loss of molten core on the way down. Overall about the same.
Destruction pvp also has its tradeoffs. Molten skin and aftermatch make things a little better but no more stuns from pyroclasm.
Overall
It looks like Blizzard wanted to make the specs more equal which is what happened here. While affliction was beating out destruction and demo for dps, when compared to other classes like hunters, mages and warriors, affliction really wasn't too strong so much as destruction and demo needing to be brought up to par. It's a shame that affliction had to be nerfed to be put on equal footing with demo and destro.
I'm most surprised that warlock pvp didn't get touched much. Molten skin and glyph of soulllink are minor positive changes but overall the removal of siphon life leaves warlocks much worse off in pvp which I think is unfortunate.