During my first attempt at Nightmare (Solo), I managed to reach Act II Belial at level 42 with no success in beating him. After several wipes, and my ego crushed, I decided to try Belial (Nightmare) solo later, and to level up in coop-mode for the first time. Several hours later, and few long naps forward my monk character level 49 finally beat Diablo (Nightmare) coop.
At first, I thought it was a bug -- the achievement was listed, but I couldn't queue to Act 1 (Hell) coop. Apparently you can queue when the character reaches level 50. Hope that helps those lvl 49 wondering what happened.
When playing a Monk, one goes with the dps mentality. The key to victory against a final boss (coop) for a monk rests mostly on the healing role. Healing other players shall be your calling as a Monk. I'm a Holy Paladin in World of Warcraft, thus it's part of my mindset to keep everyone alive. In my first attempt at Diablo (Nightmare) I went with the retribution paladin mentality, and died miserably oh-so-many-countless times.
Someone whispered me to join his group. He said I was pretty good at healing him in a past group. He needed me to help at his Diablo (Nightmare) encounter where he had wiped a few times. This time I came forth with the healing mentality. Healing in Diablo is very different to World of Warcraft healers. In WoW I can target a player and heal them from 40 yards away.
In Diablo III, it's trickier. Use Mantra of Healing with Circle of Circular Breathing (regens 3 spirit per sec -- thanks leephus) so that you don't have to hit a mob to regen spirit. Run around to stay out of harm's way if death is too often an issue with a specific boss, and run at low-health players to heal them. The catch: The Monk's Breath of Heaven skill requires you to stand within 12 yards of the low-health player to heal him. It works like an AOE.
After a lot of hit-and-run strategic heals, Diablo (Nightmare) died.
I can now queue for Act 1 (Hell) in coop mode. Played 62 hours according to my profile.
I think the developers still need to tune up some Nightmare Champion mobs or set conditions/rules for what type of random abilities they can't have at once. The death rate is really high. Jay Wilson teased you will die, and he delivered. Except, some Champion mobs are impossible to beat.
Some are simply impossibly hard to beat. Examples:
Arcane Vortex: In this situation three arcane energy lines rotate 360 degrees. Adding vortex to a boss that can do arcane means no matter how quick you are at running away from the arcane lines, the mob is going to magnetic pull you back toward him right in the middle of the arcane lines. Guaranteed death. Rinse and repeat until the three Champion mobs die. 50 deaths if you are lucky. A full armor repair cost ranges around 1800 gold. Be ready to spend a lot of gold in repairs.
Hammerhead: These are the tallest mobs in the game. If you manage to find three champions, prepare to wipe at least 100 times. Their lengthy arms are moved upwards and smash. Other than the visuals of them moving their hand upward there is no alert they will smash. The movement is too fast. Add three champions and virtually no melee player can survive or run fast enough to avoid the smash. The developers either need to increase the time of the smash animation to allow melee players to move away, or remove the unit altogether from the champion list.
molten, arcane,plague + jailer,vortex,waller: A champion pack (3) with any combination of these spells is a guaranteed 10-25 deaths before beating the champions, if there is any possibility of defeating them (depending the combination of skills). Basically, all three champions spamming will make melee players unable to even approach the champion to damage them. The jail/vortex/waller variant with any combination of molten/plague/arcane is depressing.
Other situations I observed in Nightmare difficulty:
During the Diablo (Nightmare) fight he creates clones of the players. The Barbarian has a Mortal Kombat Scorpio-like ability where he throws a chained-harpoon at the player and pulls toward him. This doesn't allow you to run away. Not sure if this one should be looked up. We beat Diablo (Nightmare even with that)
Bosses like Rakanoth or champions with charge ability: One-hit-kill with no sound/animation warning is not fun for melee players. Charge ability has no place in the game for mobs that can literally kill you in one hit.
While there are some things that cause one to complain (see examples above), the gameplay is very fun and engaging in solo and coop even with strangers. Everyone has been kind to go out of their way to resurrect me, even Barbarians. The social aspect is definitely the best. I haven't seen anyone yet yelling at someone else for messing up. I get invites from people I don't even remember playing with asking me to help out in their run.
Diablo III feels like a game you would want to come back everyday or a few days a week depending on your real life schedule. I can see people switching back and forth between World of Warcraft and Diablo III. You can leave a Diablo III game at any time, and the system automatically invites more players to replace those that left. Blizzard still needs to make some server tweaks due to a problem where only two players get to play throughout the game instead of five -- but it's something a representative recently said is in investigation.
Most times, new people join automatically when someone leaves the group. Boss encounters in Nightmare difficulty are not easy cake. It requires team efficiency and patience. The encounters can be a bit lengthy. I spotted new abilities added to Nightmare bosses, that I didn't recall seeing playing solo in Normal Difficulty.
My view for what Diablo III gameplay should be is: "Mastering your skills to prevent death, and to defeat the enemy is more satisfying." In the situation of champions that kill you in one-hit, I'd like to see new sounds or visual effects or animations in Champions to warn you of an impending attack, and to learn and implement skills to counter certain boss/champion attacks. Dying 50 times until the champion is dead doesn't seem like a fun option for melee players who need to close in to damage the champion. As soon as you close in you die on three Hammerhead champions you die instantly. No chance to run away and prevent death. There was only one range class (Wizard) doing damage to the Champions -- in my experience.
It's been a week since Diablo III retail went on sale. I haven't seen a single patch yet, but now with millions of players simultaneously some of our complaints and observations will reach the developers, and they will take care of these via patches.
Very important: Blizzard can't fix something if you don't voice your concern with a comprehensive description of the problem. Make sure to explain the situation in a calm and logical tone (i.e. avoid insults, sarcasm, slurs, and other type of tone that might get you banned or ignored). Your point is valid, just make it gentle and with good manners. Submit bug reports at the Bug Forum.
I'd love to forward Bashiok your personal feedback on Nightmare Difficulty -- whether it's complaints about certain champion ability-combinations (i.e: arcane+vortex, molten+arcane), bugs or other concerns. Post your comments below.