This is my first theorycrafting thing I've done so don't be surpised if there are some things missing.
Here it is: http://wotlk.wowhead.com/?talent=IVZf0cZxVGVr0tVoAfct
Key Talents that are new are :
Molten Core- Shadow spells and DoTs have a 10% chance to increase Fire damage by 10% for 6 seconds.
Backdraft- Increases critical chance of Conflagrate, Immolate and Shadowburn by 10%.
Kindling Soul- Your spell damage is increased by 10% of your spirit, in addition spell crits increase your Spirit by 30% for 10 sec.
Empowered Imp - Increases damage done by your Imp by 15%, all critical hits done by the imp have a 60% chance to make YOUR next spell a crit. This effect lasts 8 seconds.
Eternal Flames- Your Searing Pain and Incinerate spells have a 100% chance to refresh the duration of Immolate. In addition Searing Pain/Incinerate increase damage done by Immolate by 5% stacking up to 5 times.
Chaos Bolt- 990-1256 Fire damage, cannot be resisted. 8 second cool down, 1.5 second cast.
The idea of this build is to have as many of these effects up as possible, while keeping Immolate up and stacking Eternal Flames. You will have your Imp out attacking to get the Empowered Imp buff. Since the Imp can run out of mana quickly, we may have to plan ahead for the best times to use this, or save it for times where the boss needs to be burned down quickly.
An example of a fight could go like this. Put up Corruption and Shadow Bolt until Molten Core procs. Then put up Immolate. Now you have a choice, you can either put up 5 stacks of Eternal Flames or go for the Imp SB buff, while keeping Immolate refreshed. Another idea is since the Empowered Imp buff lasts 8 seconds and the Chaos Bolt CD is 8 seconds, trying to get a Chaos Bolt off with the crit buff up could be worthwhile. I'm not sure if a Shadow Bolt or an Incinerate would be better off here but you are also relying on the Imps limited mana.
I have never used the imp for firebolting past level 10 so I'm not quite sure on how much he can dish out with his mana. Empowered Imp seems questionable, but I dont see a reason not to have it if your not going to have any other pet out. I tried remaking the spec to include DS but it was missing a few key talents. Who knows, maybe we will get some new spells or even a new pet that changes things around.
If you have any comments or ideas, please post them.