To put Sablenite Blissey in context, let's do some number crunching!
Chansey has a base Defense of 5. After taking into account EVs, IVs, the bonus +5 to everything other than HP/+10 to HP every Pokemon has, Chansey (or indeed any Pokemon with any non-HP stat that you fully invest in) can be said to have 49 and 1/2 extra base Defense. This puts Chansey at effectively 54 and a half, +50% from Eviolite. (So slightly over 80)
Blissey has a base Defense of 10. Sablenite adds
50 Defense to that, in addition to the 49 and a half I've already covered as a given -placing Sablenite Blissey at just short of 110. That's a roughly 25% increase in Physical bulk over Eviolite Chansey!
This also means that Mega Evolving nearly doubles Blissey's Physical bulk, so be
really careful about switching it in on anything that could plausibly smack it with Superpower or whatever before you've actually Mega Evolved it, or else it's gonna
hurt.
Ok, can we please talk about banning slowbronite for the absolutely unreal bulk it provides? Adamant Diancite Terrakion. Reaches 189 attack.
252+ Atk Terrakion Close Combat vs. 252 HP / 252+ Def Blissey: 474-560 (66.3 - 78.4%) -- guaranteed 2HKO
Not even close. This shit has to go. I think blissey should be banned because anything with significant defense increases makes it broken (also chansey), and slowbronite should also be banned because it provides a ton of excess bulk that makes it extremely hard to break stall teams. When you have to hit mons with super powerful SE stabs just to try to kill them, you have a problem.
I'm not as concerned about Slowbronite Blissey as I am about Sablenite Blissey, as Magic Bounce protects it from non-Mold Breaker Toxic. (Which is admittedly two different Mega Stones) Slowbronite Blissey can, of course, use Heal Bell to cure Toxic, but Heal Bell runs out of PP well before Toxic does, so the lack of protection from Toxic severely impairs it.
Also Diancite is not the best example to use for Pokemon that already have high Attack. Have some better calcs!
252+ Atk Tough Claws (Aerodactylite) Terrakion Close Combat vs. 252 HP / 252+ Def (Slowbronite) Blissey: 554-654 (77.5 - 91.5%) -- guaranteed 2HKO
252+ Atk Adaptability (Lucarionite) Terrakion Close Combat vs. 252 HP / 252+ Def (Slowbronite) Blissey: 568-672 (79.5 - 94.1%) -- guaranteed 2HKO
Gosh, if Blissey runs Slowbronite
and maxes its HP for some bizarre reason it can reliably avoid the OHKO. (Without maxed HP, presumably maxing Special Defense, OHKOs become a possibility) Not even getting into hazards support or any other form of residual damage. Why is this a problem, exactly?
I'm also unwilling to get into any bans until the meta has more fully formed. Sablenite/Slowbronite Blissey are both amazing, but so many offensive threats are completely obnoxious too, with many solid Pokemon from OU effectively supplanting their usual, meh Mega Evolution with a much better one (Aerodactyl can run Pinsirite or Salamencite and have a real Flying STAB, instead of having Tough Claws provide almost no benefit), and many already amazing Pokemon getting a Mega Evolution
of their choice that is +100 to their BST, possibly tailoring their typing, and letting them pick their Ability.
I actually believe
Ghoul King that mono types are still programmed as (for example) Electric/Electric, but don't quote me on that. I seem to remember the community freaking out when they saw Ice/Ice M-Glalie in the ORAS Demo code before realizing this.
Also, what is the best moveset for Mega Ray Smeargle? A neat fact is that it gains pseudo-resistances to Electric, Ice and Rock, which is cool I guess.
I have been digging around all over the place, but nobody seems to care about the internal mechanics of Pokemon type designation in a readily google-able format. :(
And Delta Stream only removes Flying type vulnerabilities. Smeargle gets nothing out of Delta Stream except the ability to override other weathers. It has surprisingly decent offense, though, when backed by a Shell Smash, STAB or no, and since you're using a moveslot rather than an item slot you can actually take a Focus Sash to live on turn! And you get STAB Extreme Speed!
I'd probably run something like Dragon Ascent/Extreme Speed/coverage or support (Spore, V-Create, etc)/Shell Smash while holding a Focus Sash if I want to run Dragon Ascent Smeargle. A more traditional Smeargle build -one Baton Passing or the like rather than attacking- is probably better off with Banettite (Prankster, though there's so many things that will want that) or Sablenite. (Huge boosts to its awful defenses and Magic Bounce) Audinite could also be OK for the added Fairy typing and good defensive boosts, if you desperately want Sablenite on something else, or just want to eliminate your Fighting weakness.