Halion 10man heroic is down! I stupidly forgot to fraps it, so I sadly do not have a video, but I'll try to remember to grab it next week. We'll be working on 25m heroic this week and will hopefully be seeing a kill shortly! Phase 3 is the clincher - apart from good coordination in the Twilight Realm to avoid the cutters and good communication by your dps to keep both realms balanced, the combustion/consumption void zones are really critical. The worst we found was when two randomly ended up being placed on top of each other - the combined damage from both zones and the slow from the consumption zone was a serious killer.
Once getting the coordination down, we next had to avoid the enrage timer (which is 8 minutes). Popping heroism at the very start of the fight to push into phase 2 bought us some crucial extra time which gave some leeway when either the Physical or Twilight realm had to slow dps to even out Halion's corporeality in phase 3. As the healing is so light in phase 1 on 10 man (no adds in 10 man heroic), the healers threw in some dps as well to help push it. The timing of starting phase 3 also seemed to matter with shaving extra moments off - the faster we were able get the Physical Realm team up and dpsing, the easier it was to keep both realms balanced right away and push to the finish.
One last screenshot with the Heroic skull on the portal :D Difficult to keep both Halion and the portal in one shot, but you can see him up ahead in this one.