Alright guys. Upon much deliberation and crunching numbers / hypothesizing various scenarios, Mekkah and I have come up with a new spread. Gothic_Togekiss, this means that Mekkah and I are both submitting this spread, meaning our separate ones should go down.
120 HP / 70 Atk / 105 Def / 95 SpA / 90 SpD / 60 Spe
Now, I have discussed the reasoning behind the general theory for our spread ad nauseam...yet for the sake of the CaP Project, I shall reiterate ;)
Also, we decided to emphasize round numbers, simply because it makes calculations easy and it is staying consistent with GameFreak's general trend. Note I said general, as I know it does break this occasionally.
120 HP / 105 Def / 90 SpD allows for an extremely interesting mixed spread:
252 HP / 136 Def / 120 SpD, +Def Nature yields 444 HP / 308 Def / 246 SpD.
252 Atk Adamant Choice Scarf Outrage from Garchomp only has a 43.26% of 2HKOing this spread AFTER Stealth Rock (yes, 25%).
252 SpA Timid Life Orb Shadow Ball from Gengar only has a 43.26% chance of 2HKOing this spread AFTER Stealth Rock (yes, 25%).
Summary? A Stealth Rock weakness does not hinder its ability to be the best mixed wall in the OU game after Cresselia (and arguably Registeel...though that is a serious stretch).
OK, well Cresselia is a better mixed wall statistically, doesn't have a Stealth Rock issue and has Levitate (I am going to have to ignore the ability on our Pokemon, as it could go to any of about 15 different abilities).
What separates our Pokemon Cresselia in terms of mixed wall / support ability, however?
Cresselia's viable support options include Toxic, Thunder Wave, Reflect, Psycho Shift, and Moonlight.
I think it is safe to assume that our Pokemon will have access to Stun Spore (inferior Thunder Wave), at least one of Reflect / Light Screen, Leech Seed, Will-o-wisp, Toxic, and Lava Plume. The Leech Seed + Will-o-wisp itself makes me feel that our Pokemon's support options are superior to Cresselia's; at the very least, it gives this thing a separate niche, and allows, in some facet, to make up for being inferior to Cresselia statistically in terms of mixed walling.
Well that was a basic summary of the defensive prowess and reasoning behind our specific numbers for our spread. What about the offensive numbers?
I think I summarized quite nicely what the direct counters to this Pokemon are; Togekiss and Tentacruel for sure, with Aerodactyl and Crobat being slightly less reliable. There was also a list of extremely hazy "checks."
My reasoning for lowering its Speed to 60 is to ensure that Tyranitar, the best "check," remains the "best check." 4 direct counters is a bit low, especially if half of them are sketchy at best. Increasing the set of viable "checks" allows us to remain confident that our Pokemon will not be broken. That's why we have decided to remain stringent on the 60 base Speed bit.
OK, now for the attacks. 70 Atk / 95 SpA
I know I said 73 Atk, was cool, and it still is, but it isn't necessary.
I also ran some calculations for 70 base Atk, and at the minimum, 176, it's Wood Hammer / Power Whip would 2HKO 4 HP / 0 Def Tyranitar 97.44% of the time, and to ensure that 2HKO, all you need is 8 Atk EVs.
On max HP / 0 Def Tar, you would need 140 Atk EVs to ensure the 2HKO.
With one Swords Dance, minimum Attack (176) will always OHKO that max HP / 0 Def Tar with Stealth Rock down.
With one Howl, you would need 224 Atk EVs to always OHKO max HP / 0 Def Tar with Stealth Rock down.
For the people who want this to have the option to attack physically, with 2 120 BP moves at its disposal, 70 Atk is enough to be viable, especially with the option to add Swords Dance / Howl to its move set (I am in favor of Howl and not Swords Dance).
Now for the 95 SpA. The first thought that both Mekkah and I had was that after all that defensive, support, and surprise physical (assuming Howl / Swords Dance) potential, making its Special Attack too high would be a serious mistake. What is "too high" though? Well, obviously it is subjective, but I feel that since Gengar has the potential to OHKO this with a Sludge Bomb (Modest, 252 SpA Choice Specs Sludge Bomb from Gengar actually has a 2.56% (maximum damage) chance of OHKOing 252 HP / 252 SpD Calm), this Pokemon's Fire Blast should never OHKO an incoming Gengar. 100 SpA, or 328 max Special Attack, actually has a chance of OHKOing a 4 HP / 0 SpD Gengar, whereas 95 SpA, or 317 max Special Attack, never does.
That was, however, just a preliminary "check." I chose Gengar simply because it was the most common Pokemon with a STAB SE move against this Pokemon.
I listed Togekiss, Tentacruel, Aerodactyl and Crobat as potential direct counters to this thing. Another counter, however indirectly, is Roost Whirlwind Zapdos (assuming Stealth Rock is down). Because Roost / Whirlwind Zapdos are almost always physically defensive (252 HP 232 Def / 24 SpD Bold to have a chance at not being 2HKOed by SD Lucario's LO Extremespeed), I'll assume 252 HP / 24 SpD for calculations. The above scenario was also a bit extreme..I honestly cannot imagine anyone running a +Special Attack nature on this thing. Let's just assume 252 SpA.
Worst case scenario for Zapdos is switching into Stealth Rock and getting burned by Fire Blast. At 100 base SpA, or 299 Special Attack with 252 EVs, this Pokemon does 205 maximum damage. 384 - 96 = 288, - 205 = 83, - 48 (burn) = 35, + 24 (Leftovers) = 59. Zapdos Roosts next turn, 59 + 192 = 251, - 205 (max Fire Blast again) = 46, - 48 (burn again) = Dead Zapdos :(
However, at 95 base SpA, or 289 Special Attack with 252 EVs, Zapdos will always survive that same worst case scenario.
When it comes to ensuring that this Pokemon is not broken, 95 SpA as opposed to 100 SpA just seems to work out perfectly, both for Gengar and Zapdos.
And just for those who are concerned that we might be nerfing it offensively too much...it still always 2HKOs 252 HP / 4 SpD Suicune with Grass Knot, still has a chance of 2HKOing 252 HP / 252 SpD Careful Bronzong (always 2HKOs the standard one), and still pretty much always OHKOs 252 HP / 0 SpD Skarmory (92.31% of the time, 100% of the time with just 4 SpA EVs) with Fire Blast, all with minimum Special Attack.
95 SpA just seems to fall into our laps as the perfect Special Attack for this Pokemon, as it allows its checks and counters to remain counters and it still does its initial purposes effectively.
So there you have it, the fruits of both Mekkah's and Aldaron's labor. Our "perfect" Base stat spread.
120 HP / 70 Atk / 105 Def / 95 SpA / 90 SpD / 60 Spe
Have a beautifully serene day.