[s]wow[/s]Tigole: "Testing has been fantastic on the PTR's worldwide. You guys are doing an awesome job at identifying bugs and helping us fine tune the encounters. We still feel as though some encounters need more tuning. Because of that, we're going to put up a new PTR build sometime today or tomorrow. We've made a lot of changes to everything ranging from the average clearing mobs to many of the bosses. You'll also see a number of bug fixes in that build. ( Source )

We'll want feedback on all of the encounters. Here's a quick summary:
  • Patchwerk: Minor changes
  • Gluth: Minor changes
  • Grobbulus: Significant changes
  • Thaddius: Lots of bug fixes, minor changes
  • Gothik: Major changes. Lots of tuning and bug fixes here. Also, anti-exploit measures implemented. Please try to break this encounter and give detailed reports of how you do it.
  • Instructor Razuvious: Minor tuning changes
  • 4 Horsemen: Major tuning changes
  • Noth: Major bug fixes. Major tuning changes
  • Heigan: Almost a complete overhaul.
  • Loatheb: Minor tuning changes
  • Anub'Rekhan: Minor tuning changes
  • Grand Widow Faerlina: Lots of bug fixes. Minor tuning changes
  • Maexxna: Some bug fixes. Tuning changes
  • Sapphiron: New Spell Art improvements. Tuning changes. Bug fixes.
  • Kel'Thuzad: He's all out of bubblegum...
The community team and QA will notify you when the new build goes up on the PTR. We're also running extensive tests nightly with QA to test and tune this content. We want to give you guys a great patch. This extended PTR period (while trying on patience) will make for a better patch for everyone.

We're very pleased that so many people have shown interest in Naxxramas testing. We realize that there are still issues with Charcter Copy. These will be fixed ASAP.

We'll be on the PTR's watching raids, fixing bugs and tuning the dungeon. If you have an organized Naxxramas raid planned, post in this thread and we might come and watch you. When we watch, we often help out with repairs, buffs and resurrections to expedite testing.

We really appreciate your presence on the PTR. Your feedback is always welcome.

If you're going to be raiding, please post the Date, Time, Guild or Character name (so we can find you) and server type and location (PvP, PvE, EU, US, KR)

Thank you."

Links
worldofwarcraft.com - Source