Thanks, that makes sense. Wheel was fine without Narset, but now that I've added Narset, it might be a banwatch. I think based on that, I'll try adding Timetwister, and then might need to either ban Timetwister+Wheel or Timetwister+Narset. I'll be running Timetwister as a proxy, so there's no real monetary reason not to test and let it play for a few drafts.
I just added Narset, Parter of Veils and Sheoldred, the Apocalypse to my Legacy+ cube, and I'm thinking of adding either Timetwister or Time Spiral to go with those. I don't support Storm, and I'm already running Wheel of Fortune. Also running Memory Jar to pair with Sheoldred. I've been running Wheel mostly for Red Aggro support, but also for green ramp and artifact ramp support, so I'm thinking Timetwister since that fits into UR Aggro. But I also don't know if Timetwister is too powerful for an otherwise unpowered cube. Wheel of Fortune has been fine, but I don't know if Timetwister is any different either due to being blue or due to the shuffle letting you redraw powerful spells that were in the graveyard. I think before Leovold/Narset/Hullbreacher, the consensus was Time Spiral > Timetwister, but I don't know if that's changed now.
White Serra Paragon replacing Felidar Guardian (also Lili, Last Hope replacing Lili, Death's majesty - removing one combo from the cube. Parallax Wave and Kiki-Jiki staying)
Blue Aether Channeler replacing Mulldrifter. Sad about this cut, but I've already removed all my Man-o'-wars, and I think Soulherder will be happy to have Aether Channeler.
Land Thran Portal replacing Temple of the Dragon Queen. Dragonlord Atarka and Mutavault are the only dragons in the cube, so this should come in untapped significantly more often.
At 360, I'm running the 7 you listed plus Serum Visions. If I were to increase the size of my cube, I'd look to be adding Portent and some of the 2-mana options like Impulse and maybe Omen of the Sea.
Force of Negation is great. Both the pitch mode and the 3-mana mode are relevant. Nearly every deck in my cube has an extremely powerful sorcery speed noncreature threat. Whether that's a Planeswalker in a superfriends deck, or Natural Order in a ramp deck, or Armageddon in an aggro deck, or Tinker, or Recurring Nightmare, or Opposition, or Jitte, the list goes on. It's rare for Force of Negation not to have a relevant target. I think the pitch mode makes Force of Negation play much better than Negate, as well.
This all being said, Dimir has a lot of good cards (Baleful Strix, Ashiok, Nightmare Weaver, Psychatog, The Scarab God, Tezzeret Agent of Bolas/Schemer, Thief of Sanity, Fallen Shinobi, &c) so I am not sure if this is really needed with Hullbreacher, Narset, Leovold, and possibly Spirit of the Labyrinth in tow.
I think this is really the issue. The effect is strong, but Dimir is really stacked, and Notion Theif is weaker than other cards with similar effects (hullbreacher, Narset, Leo).
2 - Altar > Attrition. Whip depends on how much you need lifegain. The activated ability is not great, but granting lifelink can be important depending on how the rest of the cube looks.
3 - Portent > Careful Study. I'm not big on either of these, but more decks will want to play Portent.
A redundant copy of Recurring Nightmare effect. Compared to Recurring Nightmare, this has a lot going against it:
-Initial cost of 1B means the first activation costs 5 total mana instead of just 3.
-It stays in play, so it's vulnerable to Artifact removal.
-It exiles the creature instead of Sacrifice, so it's harder to do value loops
-It taps to activate, so you can only activate once per turn.
That said, there's still a lot to like here.
-2B for a 4/1 menace doesn't seem great at first, but it's 2B for a 4/1 menace that draws you a "bad" Recurring Nightmare
-The value loop side of Recurring Nightmare might be weaker here, but it still reanimates Griselbrand or other large creatures very well.
-This can still be played as a value card to bring back Ravenous Chupacabra or whatnot when those creatures die naturally, or in combination with a sac outlet in an Aristocrats deck.
-Exile hurts sacrifice of things like Gravecrawler, but this card works just as well as Recurring Nightmare with cards like Bitterblossom, Ophiomancer, and Jadar, Ghoulcaller of Nephalia.
I just added Narset, Parter of Veils and Sheoldred, the Apocalypse to my Legacy+ cube, and I'm thinking of adding either Timetwister or Time Spiral to go with those. I don't support Storm, and I'm already running Wheel of Fortune. Also running Memory Jar to pair with Sheoldred. I've been running Wheel mostly for Red Aggro support, but also for green ramp and artifact ramp support, so I'm thinking Timetwister since that fits into UR Aggro. But I also don't know if Timetwister is too powerful for an otherwise unpowered cube. Wheel of Fortune has been fine, but I don't know if Timetwister is any different either due to being blue or due to the shuffle letting you redraw powerful spells that were in the graveyard. I think before Leovold/Narset/Hullbreacher, the consensus was Time Spiral > Timetwister, but I don't know if that's changed now.
Serra Paragon replacing Felidar Guardian (also Lili, Last Hope replacing Lili, Death's majesty - removing one combo from the cube. Parallax Wave and Kiki-Jiki staying)
Blue
Aether Channeler replacing Mulldrifter. Sad about this cut, but I've already removed all my Man-o'-wars, and I think Soulherder will be happy to have Aether Channeler.
Black
Evolved Sleeper replacing Okiba Reckoner Raid
Cult Conscript replacing Gutterbones. small upgrades to the one-drop black aggro section
Land
Thran Portal replacing Temple of the Dragon Queen. Dragonlord Atarka and Mutavault are the only dragons in the cube, so this should come in untapped significantly more often.
I agree with this order.
Absence
Witness Protection
Goldspan Dragon
I think this is really the issue. The effect is strong, but Dimir is really stacked, and Notion Theif is weaker than other cards with similar effects (hullbreacher, Narset, Leo).
3 - Portent > Careful Study. I'm not big on either of these, but more decks will want to play Portent.
Altar of Bhaal
A redundant copy of Recurring Nightmare effect. Compared to Recurring Nightmare, this has a lot going against it:
-Initial cost of 1B means the first activation costs 5 total mana instead of just 3.
-It stays in play, so it's vulnerable to Artifact removal.
-It exiles the creature instead of Sacrifice, so it's harder to do value loops
-It taps to activate, so you can only activate once per turn.
That said, there's still a lot to like here.
-2B for a 4/1 menace doesn't seem great at first, but it's 2B for a 4/1 menace that draws you a "bad" Recurring Nightmare
-The value loop side of Recurring Nightmare might be weaker here, but it still reanimates Griselbrand or other large creatures very well.
-This can still be played as a value card to bring back Ravenous Chupacabra or whatnot when those creatures die naturally, or in combination with a sac outlet in an Aristocrats deck.
-Exile hurts sacrifice of things like Gravecrawler, but this card works just as well as Recurring Nightmare with cards like Bitterblossom, Ophiomancer, and Jadar, Ghoulcaller of Nephalia.