Some of these changes won't be in the initial release of the 2.4 PTR patch, but are more of a "todo-list". According to MMO-Champion's source "they're a list of changes that Blizzard will like to experiment on the PTRs. You won't see them in patch notes until Blizzard decides or not to test them on a PTR build."

Anyway, they do look very interesting.

Druid
* Cyclone range reduced to 20 yards, down from 30.
* Lifebloom healing coefficient reduced by $
* Natural Perfection now reduces damage by 2/3/4% down from 1/3/5%
* Tree of Life: You may now cast any Restoration spell in this form.
* Improved Tranquility: Now also reduces the mana cost of Tranquility by 10/20%.
* Moonkin Form no longer gains 150% attack power or mana returned from melee hits, but now refunds 2% of your total mana every time you critically hit with a spell.
* Force of Nature: Treants now have a 15% chance to proc Entangling Roots on the target.
* Nurturing Instinct: Increases your healing spells by up to 50/100% of your Agility, and increases healing done to you by 25/50% of your Attack Power.

Hunter
* Improved Mend Pet now has a 50/100% chance to remove one Curse, Disease, Magic or Poison effect, up from 15/30%.

Mage
* Blink mana cost reduced roughly 40%
* Improved Blink now increases the distance you Blink by 15/30%, and you have a 15/30% chance to reduce the cast time of your next Fireball, Frostbolt, or Arcane Blast spell by 50% after you Blink. (Might just do one of these effects…)
* Prismatic Cloak now reduces damage taken by 3/6%, up from 2/4%
* Mana Cost of Slow reduced roughly 40%
* Arcane Fortitude now increases your armor by an amount equal to 100% of your Intellect, up from 50%.
* Mana Shield now scales with spell damage. (Max rank with full S3/best gear will absorb around 1Kish, added damage absorb doesn't cost/consume mana to the shield, it will always cost what the tooltip says)
* Improved Fire Ward is now Molten Shield
* New Talent: Molten Shield – Reduces all damage taken by 2/4% while using Molten Armor, and causes your Fire Ward to have a 25/50% chance to reflect Fire spells while active.
* Frost Warding: Chance to reflect Frost spells while Frost ward is active by 25/50%, up from 10/20%.
* Icy Veins no longer increases the chance your chilling effects Freeze the target, but now reduces pushback by 100% for 20 sec.
* Icy Veins spell haste bonus no longer stacks with Bloodlust.
* Ice Flows now gives you a 15/30% chance to avoid interruption caused by damage while casting any Frost spell.

Priest
* Mana Burn effect reduced roughly 50%.
* Mana Burn cast time reduced by 1 second.
* Improved Mana Burn: Now increases the amount of mana burned from your Mana Burn spell by 10/20%.
* Focused Will now reduces damage by 2/3/4% down from 1/3/5%
* Lightwell: Charges increased to 15, up from 5.

Paladin
* Turn Undead no longer fears the target, and now incapacitates it.
* Turn Undead now works on demons. (Prob will be renamed to a diff spell)
* Turn Undead is now subject to diminishing returns.
* Turn Undead now lasts 10 sec. in PvP.

Rogue
* Envenom no longer consumes the Poison applications.

Shaman
* Lightning Bolt: Spell coefficient reduced by $
* Lightning Overload can no longer proc on instant cast spells. (aka NS+CL won't proc it)
* Lightning Overload can no longer critically hit.
* Tremor Totem and Poison Cleansing Totem now pulse every 3 seconds, down from 5.
* Earth Shield mana cost reduced by 50%
* Earth Shield now has 6 charges, down from 10.
* Healing Grace: Now also reduces the chance your spells will be dispelled by 10/20/30%

Warlock
* Life Tap: Spell coefficient reduced by $
* Life Tap now consumes toughly 10% more health when used.
* Demonic Knowledge now increases your spell damage by an amount equal to 4/7/10% down from 5/10/15%
* Improved Shadowbolt: Now only works for the Warlock.
* Improved Shadowbolt: Now increases Shadow damage by 3/6/9/12/15%, down from 4/8/10/14/20%
* Incinerate spell coefficient increased by $

Warrior
* Endless Rage now properly generates 25% more rage from damage dealt (previously only 12% cause of a bug)
* Improved Hamstring: Now has a 10 second cooldown.

Items
* Mystical Skyfire Diamond now reduces the next spell cast by 20%, down from 50%. (It also might just be changed to straight stats, still in debate. Don't be surprised if this metagem just gets added stats with the current effect in the initial 2.4 notes, it's still being worked on.)
* Shaman Gladiator 4-set bonus now reduces pushback by 30%, down from 70%.

The blue posters continues to explain some of the confirmed changes, a few of them can be found below.

Spell haste and Global Cooldown (Full post)
"With haste gear you can work toward lowering the GCD down to 1 second, but it will take more than just gear to max it."

Raid UI changes (Full post)
"The Raid UI now can display the range of players relative to you. The option to enable this is in the Party & Raid section of the UI Options."

Source: MMO-Champion