Okay I hate to be amongst the 1000s of whom post their ideas for a new hero class. But this is indeed something I and a mate have been discussing at length for a bit now. Based on the current trend, blizz will likely release a new hero class next expansion. So my idea is the Dragon Magus.

The Lore behind the idea: Many speculate Cataclysm's end with Deathwings final defeat at the hands of Thrall, the reamining aspect, Kalecgos and mortal adventurers. Traditionally, although charged to protect and watch over the mortals of Azeroth by the titans, the dragons have always considered themselves vastly superior and so have refrained from having much to do with them. However this has changed, particularly as of late. With deathwing's demise however, I feel the dragons shall finally realize our potential as both magic users and allies. So the lore is essentially. The dragons have seen our mages are far stronger than estimated, and of course the dragons decide the mortal races are worthy of learning their magicks, feel the mortals will not only be more capable of defending themselves but also more capable allies. Kalecgos, has also giving the mortals his blessing. Not only to atone for malygos' wrong but also because he has finally realized just what anveena saw in the mortals having been willing to sacrifice herself.

Specialisations: I don't have final names, merely placeholders and ideas.
#1: Manipulation. This is a frost + arcane type spec themed around The blue and bronze dragon flight and their ability to manipulate magical energies and time respectively. The frost aspect of it comes particularly from the blues, given their home in northrend and their ability to use frost magic. I suppose it can work best as a Tank/DPS similar to a Druids feral spec. Using frost they have alot of extra mitigation as mit. Is typically linked with frost with other classes. They have greater defenses, solid dps, easy to sustain. They will typically the dps choice for pvp.
#2: Restoration/Preservation. I don't really want it to sound like yet another copied spec. It will focus around alot of self healing and based around the red and green dragonflights. The reds are assosciated with life, the greens to my knowledge were using druidc type magic since before the Druids even. It will be tank/healing. A tank in this spec will simply work like a DK in terms of mitigation and self healing. Solid threat and won't die too easily. Healers will ufortunately just be another spec loaded with hots and what not. Though I'd like to see slightly weaker healing than other specs but get more 'smart healing' to assure equivalent HPS to other healers. I won't go into to much more detail. Don't assume this is going to be op, or terribly weak. It's purely an idea.
#3: Annihilation. This is also a placeholder name. It will be based for the most part on the black dragonflights with a sub theme of the red dragon flight. Fire and Shadow damage. Pure dps. This will be the stronger and harder spec. Mistakes are more costly however making both this and manipulation equally viable and probably return the same dps for most end game raids. This will work somewhat like the destruction warlock. It will revolve around monitoring shadow and fire debuffs. But rather than using alot of casted spells it will use mostly insant casts and revolve moreso around random procs and cooldowns, but I assure you will not play like a wrath ret paladin in which you can sit there with no damaging spells to use or play based off whatever pops up first. This spec will cause haste to be generally a weak stat due to instant casts. But this will be the case for all specs. Just more so this. Every class had a weak stat, and I think most cases value haste too heavily over crit for example.

Playstyle:
Essentially, this will play similarly to other classes but at the same time be unique. It will heavily rely on cooldowns and instant cast spells having a larger spell variety than other classes by a moderate amount. Being based off dragon magic. I wish to make the class seem incredibly versatile and flexible. Dragons don't particularly need to worry about being worn out. Mana will be the resource of the class. But with the exception, of healing mana will work more like a warlock. Isn't an issue. Quickly regenerated. The class will use shields and blessings of the dragonflights and their corresponding aspects. These shields are used to help enhance the role they play. Buffing mitigation, threat. And yes even for the sake of our new Mage tanks, reducing pushbacks to 0 for the few spells tanks actually cast. Some empower spells, damage and even mechanics altogether.

Disclaimer: This is merely an idea I wanted to share with you all. I do sincerely hope blizz take it on board. I might post on official forums sometime in the future. But please do post constructive critisism and give me more ideas or even your opinion