Well, less than 24 hours after receiving the patch, Ensidia downed the Lich King on 25 man. Less than 8 hours after killing the Lich King, Ensidia was banned, stripped of their loot, titles, achievements, and most importantly, their Heroic Attunement. Chaos ensues. One of Ensidia's shadow priests, Muqq, posted a profanity laden ragequit blog post. Hilarity ensues.
The root of the problem stems from a mechanic in the Lich King encounter in which he blows the outer rim of the platform away, leaving you with a much smaller area to work with. This creates problems due to a spell he casts called Defile, which is an persistent AoE akin to the slime puddles on Professor Putricide. This AoE grows larger anytime it damages someone, and if one watches Blood Legion's 10 man kill vid, you can see that it can eat up a huge chunk of space. In addition to being awesome, the Lich King's removal of the rim forces dealing with the defile to become much more urgent. Furthermore, he occasionally spawns Valkyr that grab raid members, and throw them off the side of the platform if they are not killed quickly.
The manner in which this is accomplished is similar to how the coding manages the walls and towers in WG. They're constructs, immune to all but a single type of damage, siege damage. Siege damage is only provided by vehicle abilities, and certain explosive items. The Lich King triggers a toggle which shifts the construct's animation state, causing the floor to fall out. What made things interesting was that apparently, further siege damage caused the toggle to pop again, making the lost space magically reappear. Suddenly, defile becomes much less of a problem, and even more importantly, the valkyr now simply drop their victims onto the outer ring, eliminating the need to burn them down.
There was a similar issue in Ulduar where a few guilds managed to steamroll Yogg by dropping the Vehicles from the Flame Leviathan fight through the floor, and into Yogg's room. So, now the question becomes, where did the siege damage come from? There's one vehicle source of siege damage in ICC, the cannons in the gunship encounter. However, those are mounted on rails, and cannot be moved. The other method is from the engineering profession. Saronite Bombs deal siege damage, and can be thrown often during a fight by anyone with engineering over 410.
So there's how it happened, the next question is what exactly did Ensidia do take advantage of this exploit. Some people have claimed that the Armory shows that multiple members of the raid group powerleveled engineering in the gap between the ten man kill, and the 25 man. There's also the fact that their 10 man kill shot was very oddly cropped, with basically an eighth of the screen blacked out. They also claimed that it was not anything that affected any of the difficult portions of the fight. These kinda sent warning flags up.
Further damning the raid was the fact that Blizzard, in the email sent to muqq, specifically cited that they were bugging the encounter with intent to make the fight easier. Given the black out of the chat log, the refusal to give out a fraps, and the fact that Blizz can monitor anything said in the game client, it seems reasonable to believe that Ensidia slipped up and broadcast their knowledge within the client. Throw in their history of glitching cutting edge encounters, C'thun, Vashj, Eredar Twins, Hodir Hard, Mimiron Hard, among others, and Ensidia faces a tough road trying to ask for the benefit of the doubt.
Regardless of weather or not their glitching of the encounter was intentional, their behavior under scrutiny is very reminiscent of Exodus, the guild that exploited their way to a world first Alone in the Dark kill. With that fresh in the communities memory, including Ensidia's own push to damn Exodus for their crimes, it's very difficult not to apply the same standard to Ensida.
The effect that this will have in the long run will be minimal. If Blizz has their shit straight this time, the hardest fight will be the Lich King on heroic, which is the fight that everyone is fixated upon progression-wise. This is in contrast to Ulduar where everyone was staring at Algalon, only to realize that Alone in the Dark was exponentially more difficult. Assuming that Ensida regroups and drops the Lich King next week, they'll only be one week behind the 3 or so other guilds that have downed him so far. I would be shocked if guilds even managed to get past the gear check that Heroic Blood Queen will be the first week it's unlocked. Ensidia will have the chance to catch up.