Ok, here is what happened in our game. As DM, I was underwhelmed. The players said that they enjoyed themselves, but then again, they kicked butt so hard that it wasn't even funny. We should have played on nightmare, but it wouldn't have changed too much except possibly extending the encounter a few rounds.
We had 6 PCs and 1 companion:
Halfling Ranger
Halfling Ranger|Bard Hybrid
Human Bard
Human Swordmage
Half Orc Scout
Mul Druid Sentinel
Bear Animal Companion
So, 2.5 Leaders, 2.5 Strikers, and 1 Defender (and a companion).
I won't go into a lot of detail, but needless to say, when the Ranger|Bard used Bridge of Roots in the mud pit room, that more or less ended any significant challenge.
It did take 15 rounds for the PCs to finish the adventure, but the BBEG was killed in round 14.
The Ranger Bard only took the fire damage from the initial entire room fire blast. He never took any other damage.
About half of the PCs were bloodied walking into the mud room, mostly because they had to open the door a second time and I had a Fire Bat shift from the doorway through half of the group and hit with every attack, but that didn't last long. None of the PCs ended up in mud or lava.
At the end of the encounter, the Swordmage was in single digit hit points (having taken over 130 points of damage after resistances and temp hit points in the encounter and being healed 5 times out of the 9 party heals, they loaded up on heals), but none of the other PCs were even bloodied at the end. Not a single PC used a Second Wind or a Potion of Healing. With Second Winds and potions, they had about 160 more possible points of healing (without Dailies) left over at the end. So I would have had to do at least 400 more points of damage to manage a TPK. Nightmare mode would not have been able to accomplish that, but might have slowed them up so that they didn't win within 20 rounds. Probably not though.
The companion did fall once, but was immediately replaced.
It was pretty anti-climatic. It was hardly a challenge at all and I threw every thing I could manage at the PCs. I also rolled real well on NPC initiatives with only one roll in single digits. But, it didn't help much. The PCs just had too many daily powers, immediate interrupts, ways to heal and hand out temp hit points. In fact, the Scout player totally forgot to use his two Power Strikes and still had them at the end of the encounter.
My conclusion is that optimized PCs are just too potent for this encounter. Even a fewer number of PCs wouldn't have broken a sweat too much.
WotC should go back to the drawing board if they really want to challenge players with well optimized PCs.
