Heroic Halfus

Ah good old Halfus Wyrmbreaker. This fight is very, very simple on enhance shammy for one reason: Shadow Nova. Thanks to our wind shear we can kick Every.Single.One. And we should! That's it, there's the fight! 

Ok, ok, there is a bit more you can do. 

1. Unless Storm Rider comes out super-duper-immediately the first Shadow Nova will still be a fast cast. We have all our melee count to 4 or 5 and then start kicking and it catches the cast about 90% of the time. In the beginning I didn't go for this first kick in fear of screwing up my wind shear cool down, but once you've done the fight a few times you get a sense for the timing of the first cast and you can kick as well. 
• It's important that the first kick does land, especially if your guild is new to heorics as the tanks may not be able to survive a nova + damage from the drakes/whelps.
2. We pop heroism at the beginning to ensure extra-quick-whelp-death. Usually it's a mage pretending they're as cool as us shaman's and popping timewarp, but if you happen to be mage deficient in your raid then it falls on you to use bloodlust.
3. I assume whelps are being aoe'd down. I like to drop my magma totem for this part just to throw a little extra damage their way since dps on Halfus isn't really important at this stage. Just make sure you throw searing totem back on when you're done.
4. In the beginning everyone will be crowded in the middle, and even if they're not, their aoe's are (especially if your graphic settings making everything the warlock does look exactly the same!), so trying to dodge the fireballs is a bit hard to do. This makes it a good time to pop shamanistic rage so that if you happen to eat a fireball your healers won't hate you as much (but don't worry, they'll still hate you a little). 
5. Once whelps/storm rider are down it gets a little less crowded and you should be dodging fireballs like you're a rouge with evasion on. 
6. As for feral spirit, I pop it once in the beginning and then it's up again in time for any of Furious Roar/push to the end.
7. Furious Roar is definitely a good time for shamanistic rage. Make sure you're aiming and jumping even as you're knocked back so you don't get stuck in a fireball.

If you want to be super pro, there is the option of setting Halfus on focus and dpsing Storm Rider along with the rest of the melee, using a macro to interrupt your focus. However, between lag and the off chance that the tank has moved Halfus and you're suddenly facing away from him, I'd say it's far better to just stick on Halfus.

As long as you are getting Every.Single.Kick. and pushing your dps as much as possible around it, this fight should go quickly. Make sure you've got Deadly Boss Mod warnings for Shadow Nova turned on - but don't rely on the sound alone as it can sometimes lag behind.