Xailter
OG
This covers multiple twinks in the 39 bracket and while I can't comment on all classes and specs I can give a pretty good general overview 
Feel free to disagree of add stuff after reading it all please!
Paladin - Holy
Overall, the health loss hasn't been too bad for me. I have 3k health with BoK still... my healing has dropped slightly but I feel my survivability is pretty much the same. I've tried both full holy (with 10 second cooldown exorcism!) as well as my current build of 12/18/0 which is a survival healer. Having exorcism (and the glyph) has meant my holy pala actually has some sort of damage these days! 600 crits were pretty nice, and while I couldn't really kill rogues I could at least hurt them for a change.
Paladin - Retribution
Exorcism here has become OP. There I said it. I've crit 850+ in my less than perfect gear. The lower health hasn't affected Ret Palas so much - they just have so much burst that they kill anything anyway. Not fun anymore - and the burst needs to be reeled in substantially - either through removal of exorcism use at lower levels or severely lowering it's base damage.
Warlock - Affliction
The damage has dropped. Not be a lot but it is noticeable. The healing recieved from Siphon Life is pretty good now (with the glyph), my Corruption was ticking for about 190 which is 95*1.2 = 114 health every three seconds which is quite handy. However they are far to burstable these days and have little defence verses hunters, rogues and paladins.
Warlock - Destruction
I haven't had too much chance to try this out yet, but it's actually really fun! Backlash being available at this level is quite fun and allows me to blast some 900 shadowbolts at people if they're silly enough to attack me! I have ~20% crit and ~30% crit with Searing Pain. The burst makes this spec viable now - go try it out if you fancy a challenge Molten Skin is also a cool addition accessible to all trees!
Warlock - Demonology
I see no reason to go full Demo since 3.1 hit - a balance of Demo/Affliction is sufficient with the new Soul Link glyph and means my Demo damage has gone up a bit which is nice. Personally the best spec for warlocks still - this spec can survive a lot of burst before finally dying - mainly because of all the defensive talents.
Druid - Feral
Feral has taken a fair old whack to it's survivability. First of all the Bear Form nerf has reduced the Druid's 'oh ****' form combined with the loss of 500 health from the leg armours and librams. They pretty much have to go for burst all the way now and act like crappy rogues which is sad.
Druid - Restoration
Nothing but nerfs I'm afraid. Regrowth crit chance nerfed, spell power and health dropped again - poison cleansing takes longer to remove poisons past the initial cast. I'm certainly feeling more killable these days; that would be why I'm currently balance specced!
Druid - Balance
Again nothing but nerfs it would seem, but the damage is still there. I'm not very comfortable running around with 2.3k health but I can still chuck out the 1.1k starfires quite effectively. Consider a switch over to balance - all you lose is Nature's Swiftness (if you have a problem with rogues that much I suggest investing in a paladin).
Hunter - Marksmanship
Damage has gone up I feel and speccing full damage is quite a viabale tactic now (full 30 points in MM). The increased damage and use of Readiness can do some insane burst (double Aimed Shot / Arcane Shot combo is insane!). Definately a viable choice for some bursty game play these days. Something like: http://www.wowhead.com/?talent#cZbeVMohzGh is very very bursty.
Hunter - Survival
Entrapment is a huge buff to hunters! Need I say more really? Lock and Load provides some nice burst and combine with Aimed Shot for good times
Rogue - Subtley
Nothing has changed except the lower health has made it easier to gib some classes. Ambush has become a very viable opener these days when compared to pre-patch.
Rogue - Daggers
Also more viable due to lower health - go give it a go if you haven't already as you may enjoy it a tad more these days.
Rogue - Combat
With a few combo points and some skill you can have 50% haste speed which quite frankly is insane verses nearly all classes. Watch those numbers fly!!!
Just some observations I've made after a bit of play testing!
-X
Feel free to disagree of add stuff after reading it all please!Paladin - Holy
Overall, the health loss hasn't been too bad for me. I have 3k health with BoK still... my healing has dropped slightly but I feel my survivability is pretty much the same. I've tried both full holy (with 10 second cooldown exorcism!) as well as my current build of 12/18/0 which is a survival healer. Having exorcism (and the glyph) has meant my holy pala actually has some sort of damage these days! 600 crits were pretty nice, and while I couldn't really kill rogues I could at least hurt them for a change.
Paladin - Retribution
Exorcism here has become OP. There I said it. I've crit 850+ in my less than perfect gear. The lower health hasn't affected Ret Palas so much - they just have so much burst that they kill anything anyway. Not fun anymore - and the burst needs to be reeled in substantially - either through removal of exorcism use at lower levels or severely lowering it's base damage.
Warlock - Affliction
The damage has dropped. Not be a lot but it is noticeable. The healing recieved from Siphon Life is pretty good now (with the glyph), my Corruption was ticking for about 190 which is 95*1.2 = 114 health every three seconds which is quite handy. However they are far to burstable these days and have little defence verses hunters, rogues and paladins.
Warlock - Destruction
I haven't had too much chance to try this out yet, but it's actually really fun! Backlash being available at this level is quite fun and allows me to blast some 900 shadowbolts at people if they're silly enough to attack me! I have ~20% crit and ~30% crit with Searing Pain. The burst makes this spec viable now - go try it out if you fancy a challenge
Molten Skin is also a cool addition accessible to all trees!Warlock - Demonology
I see no reason to go full Demo since 3.1 hit - a balance of Demo/Affliction is sufficient with the new Soul Link glyph and means my Demo damage has gone up a bit which is nice. Personally the best spec for warlocks still - this spec can survive a lot of burst before finally dying - mainly because of all the defensive talents.
Druid - Feral
Feral has taken a fair old whack to it's survivability. First of all the Bear Form nerf has reduced the Druid's 'oh ****' form combined with the loss of 500 health from the leg armours and librams. They pretty much have to go for burst all the way now and act like crappy rogues which is sad.
Druid - Restoration
Nothing but nerfs I'm afraid. Regrowth crit chance nerfed, spell power and health dropped again - poison cleansing takes longer to remove poisons past the initial cast. I'm certainly feeling more killable these days; that would be why I'm currently balance specced!
Druid - Balance
Again nothing but nerfs it would seem, but the damage is still there. I'm not very comfortable running around with 2.3k health but I can still chuck out the 1.1k starfires quite effectively. Consider a switch over to balance - all you lose is Nature's Swiftness (if you have a problem with rogues that much I suggest investing in a paladin
).Hunter - Marksmanship
Damage has gone up I feel and speccing full damage is quite a viabale tactic now (full 30 points in MM). The increased damage and use of Readiness can do some insane burst (double Aimed Shot / Arcane Shot combo is insane!). Definately a viable choice for some bursty game play these days. Something like: http://www.wowhead.com/?talent#cZbeVMohzGh is very very bursty.
Hunter - Survival
Entrapment is a huge buff to hunters! Need I say more really? Lock and Load provides some nice burst and combine with Aimed Shot for good times
Rogue - Subtley
Nothing has changed except the lower health has made it easier to gib some classes. Ambush has become a very viable opener these days when compared to pre-patch.
Rogue - Daggers
Also more viable due to lower health - go give it a go if you haven't already as you may enjoy it a tad more these days.
Rogue - Combat
With a few combo points and some skill you can have 50% haste speed which quite frankly is insane verses nearly all classes. Watch those numbers fly!!!
Just some observations I've made after a bit of play testing!
-X
