So... Last night my guild *Stands In Bad* and myself finally, on our 3rd week of semi-halfharted last minute attempts (no... that's not fair... we spent the entire night fighting him last night, and probably 2 hours previously) finally took it to Barney and gave him what for.
Yep... That's me dying at the same time Halion did... LOL oh well. We killed him and that's all that matters. How did I die? Well, I was the shadow realm tank, of course. I got so spazzed at seeing him below 100k health I turned him too fast and stepped right into a damn shadow cutter... hahahah oh well.
Now, i'm not going to post a full on strategy for fighting Halion, because that's longer than I want my usual posts to go, but I do want to give a few pointers to anyone who might be tanking in the shadow realm.
After you enter the portal at the start of p2, turn him so he's not facing it. There's nothing worse than having 7 people enter behind you right as Halion cleaves or shadow breaths, insta-killing 3 people.
Watch the orbs at all times... Whether cutters are out or not. What we ended up doing was simply rotating him the entire time in p2, so he was always in the same relative position to me, the cutters, and the DPS/Healers. This took a few tries to perfect, but I found a great point of reference where one orb along the back was right near my spell timers (in the top right corner if you look at the image) it would almost never hit me, and was really nowhere near my DPS.
If you're NOT a tank, for the love of god don't leave a soul consumption within melee range of Halion. This wasn't a *big* problem per se, but it was something that did happen a couple times. While I was rotating him, I had to turn him extra fast a couple of times so I could run through a big gaping pit of nasty on the ground. That's extra damage the tank shouldn't take, and it can be avoided.
Disc priests are <3. Seriously.. We have one priest who's dual specced holy and disc, as well as a resto druid in the shadow realm. I first thought "Go holy! That'll help with the tree deal with all the AOE damage people take in the shadow realm!"... Which it did, but it was countered by the fact that without the love of a good disc bubble, i was taking probably 1.5x the damage I normally would. And i'm a well geared tank too... but MAN was I Taking a shit ton of damage. After about our 4th wipe we had him go back to disc and all was right with the world again. Make no mistake, I was still taking a lot of damage, but holy shit the difference between a disc priest and a holy priest is just immeasurable.
And finally, my last little bit of advice...
Don't watch his health bar too much. Seriously... If you wipe the raid at 2% because you spazzed from seeing him get low health and think "We're finally gonna do it this time!", and step into a shadow cutter you will be picked on for it. My raid was amazingly understanding at the time, and sure enough our next attempt was the killshot... but still. I could've absolutely self-immolated for that mess.
Halion's a hard fight. If you're too used to that ICC buff you'll wonder where the fuck your DPS numbers went... where your health bar went... where your big heals went, etc. But aside from all that, it requires a LOT more cohesion and situational awareness as a group than all but the toughest of ICC normal mode fights... and some of the heroics too. It's definitely harder to tank (in the shadow realm at least) than any normal-mode fight in ICC is... even The Lich King.