Quote from Blizzard staff
Dual-Spec system
The dual-spec system will be introduced in a content patch. The goal is to let you switch specs very easily in raid, even between fights ! However it won't be possible to switch specs in the middle of an arena match.
With dual-spec introduced in the game, there are also discussions about an Itemrack-like mod being introduced to the default UI
Group Flexibility
There are 30 specs but only 25 spots in a raid. The class choice should be very flexible and the buff/debuff system overhaul was done to help with that. Cancelling a buff because a class wasn't available (like Shamans for Bloodlust) was not desirable.
Most buffs now affect the whole raid and multiple classes can give them, however none of them will stack. You should get more types of buffs by bringing a fewer number of players and will be able to optimize them by bringing the right spec but it definitely won't be as necessary as it was in TBC. (Note : See Raidcomp !)
Tanking
All the tanking classes are now suitable as a main tank and their threat has been greatly increased to make fights more fun, fights are now more about skills than dying because of a random aggro.
Death Knight (Skills List / Talent Calc. (9061))
The original idea behind the rune system was a totally customizable rune pool (like, 6 Unholy runes) but "it sucked". They changed it to what is it today (2 Runes of each type)
Death Knights shouldn't be played like a metronome and is intended to be an interactive and reactive class.
As a death knight, your talent trees are a good way to define "your style, but not your role". Devs want to bring this philosophy to other classes.
Druid (Skills List / Talent Calc. (9061))
Balance druids have been greatly improved and you shouldn't see a lot of OOMkins anymore. Their DPS is now on par with other DPS classes.
Balance DPS looks pretty good now but developpers are keeping an eye on the survavibility
Entangling roots was allowed indoor to give druids more crowd control ability in instances.
Restoration were stuck in the HoT niche and were very limited in 5-mans or raids. Nourish is new flash heal-like spell added to solve this problem on single targets and Wild Growth was added to give them an AOE Heal.
Druids were also given an OOC resurrection spell.
Feral druids were decent at tanking and DPSing, but couldn't master any of these fields. In WotLK you can take all the bear talents to become a very good main tank, or all the cat talents to have a very high DPS.
Feral mana is a known issue, and developpers don't want intellect on feral gear. This is being looked at
Hunter (Skills List / Talent Calc. (9061))
The hunter pet system was overhauled because it was "clumsy for new players".
The shot rataion has been cleaned to make things easier for hunters and make them less reliant on mods or macros.
Freezing shot was introduced to make pulls faster without having to deploy your traps on the ground each time.
Mage (Skills List / Talent Calc. (9061))
Frostfire Bolt is a way to achieve an elemental tree with mages, they should be able to deal both fire and frost damage
Mage DPS looks pretty good now, there are still a few mana issues getting fixed very soon
Living Bomb base damage will most likely be increased and the spell mechanics might be modified slightly. Overall, the 51-points talent weren't meant to be spammed and developpers want them to be situational
Frost and Fire looks pretty balanced now, but Arcane needs a few more tweaks. Arcane needs to be more "mobile"
Paladin (Skills List / Talent Calc. (9061))
Paladins were decent off-tanks but not great main tanks, this is fixed in WotLK. Paladins should focus on protection gear instead of spell power.
Holy Paladins were good healers but couldn't do much in encounters where players are required to move a lot, however they definitely don't want them as a HoT class.
Retribution paladins are supposed to deal a decent amount of DPS without running out of mana.
Retributions paladins have to be in control of their damage and shouldn't have to rely on lucky critical strikes to deal most of their damage
Priest (Skills List / Talent Calc. (9061))
The goal with Shadowpriest is to make them a DPS class, not just a mana battery.
Discipline priests should be viable raid healer.
Mind sear was introduced to give priests another viable DPS ability.
Class-specific racial abilities were cool, but the idea became got "old" with time. That's why racials have been revamped
Rogue (Skills List / Talent Calc. (9061))
AoE DPS was really needed and Fan of Knives was added to the game.
Purchasable poisons and the buff of the dagger spec should help "reintroducing" them to the game.
The goal is to have end-boss less immune to poisons and rogues less dependant of Windfury
Shaman (Skills List / Talent Calc. (9061))
Totems are now physical and harder to dispell, have more life and last longer.
Hex was added to give Shamans more crowd control ability, Riptide to improve their healing, and Lava Burst their spell DPS.
Warlock (Skills List / Talent Calc. (9061))
Warlocks pets have been made more useful.
The warlock rotation shouldn't be restricted to a shadowbolt spam, that's why Chaos Bolt was added.
Affliction Tree is still too complicated and developpers are working on it. Developers definitely want it back as a raiding spec
Pets should be easier to summon/switch and use.
Warrior (Skills List / Talent Calc. (9061))
Protection spec has been revamped to make it cooler to play, mitigation talents now take a lot less points and will let you invest in a few other nice tools.
In TBC, Arms was PvP and Fury the PvE spec, this will change in WotLK : Battle Stance, Overpower, and Rend have been improved. New fun abilities have been introduced like Bladestorm and Sudden Death, Fury obviously have Titan's Grip.
