I entirely understand the frustration felt by guilds that have already defeated Heroic Norushen this week, or invested significant time attempting his current incarnation. It's never particularly enjoyable to have to relearn a fight you've already defeated and from which you've already received loot and an achievement. Changing an encounter meaningfully once it's in players' hands is not an action we take lightly. I'd like to offer a few general points of clarification:
First, we did read and closely consider all feedback received as a result of Norushen PTR testing. We made a number of adjustments to the encounter as a result of both player feedback and our own observations over the course of testing. Notably, we removed the Draw mechanic that was present for most of the PTR testing cycle, since it caused players to have to throttle their damage as their gear and execution improved. That mechanic was originally added to completely shut down any chance of a brute-force approach, but we believed that the damage penalty from the initial Corruption would be sufficient to require players to use Look Within to purify themselves in order to meet the berserk timer. Clearly we were mistaken, and I'd like to personally apologize for that.
Second, we are not looking to meaningfully increase the difficulty of the encounter. It should, on balance, be a small to moderate step up in difficulty from Heroic Fallen Protectors, and should be easier than Sha of Pride. While we're still iterating on the exact changes, they will likely entail something along the lines of entirely removing the additional pulsed Corruption received from Burst of Anger and Residual Corruption, increasing players' starting Corruption to 75 as is the case on Normal, and adjusting the health of the Amalgam accordingly. We don't expect that most guilds that defeat the encounter this week will experience any notable struggles with the revised version.
Third, in keeping with the general philosophies laid out in the Encounter Tuning Dev Watercooler, a major factor when it comes to deciding whether to make changes to address an unintended strategy is whether the approach actually involves interesting gameplay. Yes, a really tight Patchwerk-style DPS check absolutely can be fun even without any other mechanics involved, and many players had nailbiting kills and wipes on the encounter this week. But in a few more weeks, with a bit more gear, that fun would largely be gone. And for the healers that most raid groups benched in order to add damage-dealers to meet the DPS check, it likely was never there to begin with. Ultimately, this is a change made for the sake of the thousands of guilds that have yet to attempt the encounter, but will in the future. To those who are experiencing the disruption of having the boss change mid-progress, I again apologize. There are many parallels to our handling of Heroic Primordius (and, yes, those parallels do begin with us screwing up the tuning in the first place).
Finally, I've seen a few references in this thread, and elsewhere, to Thok. The change made to Thok last week was entirely a bugfix. Based on our final days of Raid Finder testing on PTR, we decided to completely disable the Acceleration mechanic that increases Thok's energy generation in Raid Finder, since he changes phases based on health % thresholds in that mode. That change inadvertently removed the mechanic from all difficulties, and the 20-hour time period for which the bug was active represents the time it took us to track down the cause, implement a fix, and test that fix before applying it to the live environment. Thok's current energy regen rate is identical to the values seen for the better part of PTR testing. Had we changed nothing, Thok would have been the easiest encounter in the zone rather than one of the more challenging ones, and we are always going to fix bugs that completely trivialize raid encounters. That was a bug that we fixed ASAP. The upcoming Norushen adjustments, however, are design changes that we're going to roll out along with raid resets next week so that they affect everyone equally.