Wait wait wait.
Why the hell is Cosmic Power not listed at all?!
CP Clefable is insane, it just eats up all those hits like it's a dragon ffs.
You don't have to analyze the set or anything (Well, it would be beneficial...) but, at least mention it in the move pool. Okay? :D
Nice Revamp though, n-n
Cosmic Power is going unmentioned because it lacks the kind of power CM gets, even with Stored Power, and Clefable's a bit strapped for moveslots between needing Stored Power, Fire Move, Moonlight/Soft-Boiled, Cosmic Power, Moonblast. Without the inherent boost of CM vs CP only boosting Stored Power, Clefable has a hard time breaking Dark types (some like base Houndoom outright can't be touched and set up themselves), and is generally set-up bait/free switch-in for any non-frail target that's immune/resistant to Stored Power like Victini, Heatran, Mega Sableye, the previously mentioned Houndoom, etc.
252+ SpA Clefable Stored Power (260 BP) vs. 248 HP / 192+ SpD Heatran: 91-107 (23.6 - 27.7%) -- possible 5HKO after Leftovers recovery
252+ SpA Clefable Fire Blast vs. 0 HP / 0 SpD Mega Houndoom: 58-68 (19.9 - 23.3%) -- possible 5HKO
252+ SpA Clefable Stored Power (260 BP) vs. 0 HP / 0 SpD Victini: 125-147 (36.6 - 43.1%) -- guaranteed 3HKO
Clefable needs CM's boost if it wants to take an offensive approach, which tends to be the only way it's not outclassed in some of its roles. It's abilities let it sit against a lot of types of damage, but with Cosmic Power all it can do is sit there, sometimes waiting for a Crit or the opponent to status/set-up on it.
Boosting only defenses is not going to let you scare the opponent out, since often they will carry an offensive mon able to boost. Heck, an opposing Sp Def Clefable can use you for set-up bait while you boost and come out on top
+1 0 SpA Unaware Clefable Moonblast vs. 252 HP / 4 SpD Clefable: 160-189 (40.6 - 47.9%) -- guaranteed 3HKO after Leftovers recovery
252+ SpA Clefable Stored Power (260 BP) vs. +1 252 HP / 96+ SpD Clefable: 149-176 (37.8 - 44.6%) -- guaranteed 3HKO after Leftovers recovery
Let's assume opposing Clefable switches in on your first Cosmic Power with Unaware
252+ SpA Clefable Stored Power (140 BP) vs. +2 252 HP / 96+ SpD Clefable: 61-72 (15.4 - 18.2%) -- possible 8HKO after Leftovers recovery
+2 0 SpA Unaware Clefable Moonblast vs. 252 HP / 4 SpD Clefable: 213-252 (54 - 63.9%) -- guaranteed 2HKO after Leftovers recovery
Plus, Stored Power isn't that much better than a boosted Moonblast
252+ SpA Clefable Stored Power (260 BP) vs. 0 HP / 0 SpD Manaphy: 250-295 (73.3 - 86.5%) -- guaranteed 2HKO
+6 0 SpA Clefable Moonblast vs. 0 HP / 0 SpD Manaphy: 390-460 (114.3 - 134.8%) -- guaranteed OHKO
In the time it would take you to max out Stored Power, CM Clefable reaches the same boost in bulk, and outdamages with no investment or nature, while also getting the power boost to Fire Blast.
tl;dr
Cosmic Power Clefable is in every way inferior to any other boosting Clefable or Boosting Pokemon set. Do not use
Posting in spite of being beaten to the punch.