to B+ or B
How is it still A-? It is weak to a slew of common moves, such as Tomo's Hurricane and Astrolotl's Fire Lash and every non super-effective hit will usually KO it anyways, limiting its ability to switch in.
Zeraora: 252 Atk Zeraora Plasma Fists vs. 0 HP / 0 Def Syclant: 198-234 (70.4 - 83.2%) -- guaranteed 2HKO
Dragapult: 252+ Atk Life Orb Dragapult Dragon Darts (2 hits) vs. 0 HP / 0 Def Syclant: 296-350 (105.3 - 124.5%) -- guaranteed OHKO
0 Attack Astrolotl: 0 Atk Astrolotl Fire Lash vs. 0 HP / 0 Def Syclant: 496-588 (176.5 - 209.2%) -- guaranteed OHKO
Alakazam: 228 SpA Life Orb Alakazam Psychic vs. 0 HP / 4 SpD Syclant: 277-328 (98.5 - 116.7%) -- 93.8% chance to OHKO
to B or B-
It really is just too frail to switch in to almost any attacks. If you want a CAP fairy wall, just use Aegislash, which also offers more defensive utility.
Astrolotl withat least 164 neutral nature attack: 164 Atk Astrolotl Knock Off (97.5 BP) vs. 0 HP / 0 Def Gengar: 262-310 (100.3 - 118.7%) -- guaranteed OHKO (If you're arguing that gengar isn't common enoguh to warrant that, then that's a reason it shouldn't be B+)
Dragapult: 252+ Atk Life Orb Dragapult Dragon Darts (2 hits) vs. 0 HP / 0 Def Gengar: 336-398 (128.7 - 152.4%) -- guaranteed OHKO
Zeraora: 252 Atk Zeraora Knock Off (97.5 BP) vs. 0 HP / 0 Def Gengar: 288-340 (110.3 - 130.2%) -- guaranteed OHKO
Alakazam: 228 SpA Life Orb Alakazam Psychic vs. 0 HP / 4 SpD Gengar: 486-577 (186.2 - 221%) -- guaranteed OHKO
Hydreigon: 252 SpA Life Orb Hydreigon Draco Meteor vs. 0 HP / 4 SpD Gengar: 339-399 (129.8 - 152.8%) -- guaranteed OHKO (Focus blast only has an 18.8% chance to OHKO)
The Syclant argument doesn't make much sense, because your main argument is that its weak to Tomohawk and Astrolotl, even though neither can't actually switch in?
252 Atk Choice Band Syclant Earthquake vs. 72 HP / 0 Def Astrolotl: 386-456 (102.9 - 121.6%) -- guaranteed OHKO
Possible damage amounts: (386, 392, 396, 400, 404, 410, 414, 418, 424, 428, 432, 436, 442, 446, 450, 456)
252 Atk Choice Band Syclant Icicle Crash vs. 72 HP / 0 Def Astrolotl: 246-291 (65.6 - 77.6%) -- guaranteed 2HKO
Possible damage amounts: (246, 249, 252, 255, 258, 261, 264, 267, 270, 273, 276, 279, 282, 285, 288, 291)
-1 252 Atk Choice Band Syclant Icicle Crash vs. 252 HP / 120+ Def Tomohawk: 224-266 (54.1 - 64.2%) -- guaranteed 2HKO
Possible damage amounts: (224, 228, 230, 234, 236, 240, 240, 242, 246, 248, 252, 254, 258, 260, 264, 266)
Syclant has never been about switching in on things, its a glass cannon. Its role is to revengekill or bust up holes in walls. The rise of Dragon types, Syclant and pivoting builds in general boosts Syclant's viability since its a great means of revenge killing both, while also being an excellent fit on the latter.
A similar thing for Gengar. Gengar isn't used as a "Fairy wall". Its used as a wallbreaker that takes advantage of the fact that the list of Shadow Ball switchins are Mandibuzz and Blissey, the latter of which is set up bait for and the former can be overloaded throughout the course of the match. Also the "Astrolotl" argument makes no sense, using your spread and assuming its max speed, that attack and the rest in HP, Gengar can just spam Sludge Bomb until it gets a Poison and Astro can't consistently switch in anymore.
252 SpA Gengar Sludge Bomb vs. 92 HP / 0 SpD Astrolotl: 211-250 (55.5 - 65.7%) -- guaranteed 2HKO
Possible damage amounts: (211, 214, 217, 219, 222, 225, 226, 229, 232, 234, 237, 240, 241, 244, 247, 250)
Not even the SpD set can outlast it
252 SpA Gengar Sludge Bomb vs. 72 HP / 252 SpD Astrolotl: 153-181 (40.8 - 48.2%) -- 65.6% chance to 2HKO after poison damage
Possible damage amounts: (153, 156, 157, 159, 160, 162, 165, 166, 168, 169, 171, 174, 175, 177, 178, 181)
Again I think you miss the point of most of these mons. They aren't walls that switch in on a bunch of shit, and quite frankly your advocacy for Blissey should be rising these Pokémon up, because all they do is take advantage of it, (especially Gengar).