?? difficulty is definitely doable. I did it earlier this week after the nerfs as Sunfury Arcane (which is tuned a bit higher, so it may be rougher in other builds - not sure).
I had Brann as a healer, porcelain arrowhead / amorphous relic combo. Oddly enough, it felt easier when the relic gave me movement speed over the damage increase.
I had to make a talent loadout specifically to try to figure this out. Anything and everything defensive can help you. Tempest barrier, Diverted Energy, Energized Barriers, Flow of Time, Displacement, and Accumulative Shielding were all taken and used. Greater invis is unusable, so don’t bother with any of that. Same with anything AoE or Crowd control. They’re theoretically not necessary, but Blast Wave or Supernova / Dragon’s breath could be useful if you fail to break an egg.
The same rules on ? apply to ??. Dodge everything or you lose. You might survive a hit from some of the abilities, but it’ll go downhill quickly if you messed up
Do your best to break the eggs, but even if you fail, the spiders spawn with less health proportional to how much damage you dealt and can be finished off if you just barely missed it. But the important thing is you cannot afford to use your interrupt on the adds. Blast wave and supernova / gravity lapse will be your friend. You might even be able to stop their cast by polymorphing them quickly - just make sure you can break them out before the heal ticks too many times. It did also feel like the spiders don’t spam cast anymore. So if one does break out, you might be able to sit in an ice block until it gives up.
Counterspell needs to be saved for his heal. The dot damage isn’t great, but you can clear it from you with Energized Barriers. That means you can’t be casting your shield on cooldown. You will need to let him punch you in the face, unshielded, until he casts the dot. Then and only then can you put your shield up (to clear the dot and get your shield).
His melees still aren’t great, but they’re livable. Don’t be afraid to spend more time trying to kite and less time beating him up. Making use of Blink / Alter Time / Displacement (especially for the heal) can let you zip across the room and get a few seconds of reprieve - just be careful because the frontal is wider the further you are from him, so don’t strand yourself.
Oddly enough, I found his phase transition at 60% to be easier than the first half. I popped hero on pull to try to get to that phase faster. He does go immune during the transition. I managed to get an egg to spawn right around 61%, so I transitioned him and focused on the egg while he RP’d. After the transition he adds a rather long “don’t stand in the brown swirlies” channeled ability to his repertoire - but he’s casting the entire time it’s happening. Good use of ice floes or any other mobility makes this pretty trivial, so you can get a lot of good damage out without needing to worry about being hit.
He does start spawning portals with some abilities now, but I’m going to be fully honest with you all: I never quite picked up on how they work. I assume it’s “Don’t touch them” and “don’t stand in line with them” because I’m pretty sure they shoot orbs out of them. But I managed to get the kill without worrying too much about them, so if you’re having trouble with that part, I can’t help you.
All in all, post nerf, it did take a bit to get into the flow, but certainly not as much time as I spent pre-nerf. It’s one of those things where a single mistake could easily be the end of an attempt - you just need to make note of the mistake and give it another shot. Don’t be afraid to grab some verse food / flasks and make sure you have Healing Potions. Cavedweller’s Delight is also considered a combat potion, not a health potion, so they don’t share a cooldown with each other. If losing health is a bigger issue than dealing damage for you, use the delight instead of an offensive potion. It’ll save you money, too.