Okay, so after a long week of vacation I'm finally back at it! Let's see what we've got here.
Agent Gibbs
You probably won't add every E rank pokemon because that will take too much work and the pokemon in this rank are so niche that they probably don't need to be added here. However, I would add both Nidoking and Nidoqueen because they are D rank now
Yeah, I probably won't go through the entire E Rank for checks at the moment since there's just so much stuff there, but I'm perfectly fine with adding E Rank Pokemon as checks if there's any that will fit. Like I said in the OP, I want to include as many options as possible when discussing potential checks within reason. I've kinda got the same mindset that CTC did where I think you should always keep your options open to even some of the more unusual choices since you never know when that one random lower tier Pokemon will fulfill just the right niche on your team. I still want to keep it within reason, though (so no Ferroseeds, sadly), but E Rank is plenty reasonable enough.
That said, I've added your Nidoking and Nidoqueen stuff. Thanks!
Also how do multi hit moves work when considering GSIs? From Mega Venusaur being listed I'm assuming we are standardising it to 3 hits. But;
240 Atk Life Orb Mamoswine Icicle Spear (5 hits) vs. 252 HP / 240+ Def Thick Fat Mega Venusaur: 170-210 (46.7 - 57.6%) -- approx. 94.9% chance to 2HKO
I guess getting 5 hits twice (or 4 and 5 + SR), is sort of disregarded as is critting right? Due to unlikely hood?
Yeah, that's actually a good question. I used Icicle Crash for the calcs since it's considerably more common than Icicle Spear and it's much simpler. Multi-hit moves are tricky, though. Forgive me while I think out loud for a second.
Okay, so the chances of hitting a certain number of times have the following percentages: 2 hits = 33.3%, 3 hits = 33.3%, 4 hits = 16.7%, 5 hits = 16.7%. Assuming we're just talking about 2 Icicle Spears in a row, let's look at the probability that Mamoswine gets 9 or 10 hits. The only events where this can happen are with 4+5, 5+4, or 5+5. Given the above probabilities, assuming I'm doing my statistics right, the probability of any one of these events happening is 0.167*0.167 + 0.167*0.167 + 0.167*0.167 = 8.37%, which is only slightly higher than the chance of a crit and not even as high as the chance to get a random freeze with Ice Beam or something. Not too much of a concern. Now, if we include the possibility of 8 hits, we also have to include the events 3+5, 5+3, and 4+4. Therefore, the chance of Mamoswine getting 8 or more hits is 22.3%, which is much more of a concern.
Since the probability of getting 9 or 10 hits is much less significant and therefore a lot easier to dismiss, maybe we can say that a Pokemon just has to be able to survive at least 8 hits to be a GSI. That said, defensive Mega Venusaur is only 2HKOed ~9% of the time by 8 Icicle Spear hits after Stealth Rock, which is even lower given the chance of actually getting 8 hits, so I guess it's uncommon enough that Mega Venusaur is okay as a GSI. Maybe not though, I'd like a second opinion on this lol. Also on if 8 hits should be the benchmark of if it should be lower/higher.
There's also the possibility that I really screwed up my statistics and this is all wrong, but it is what it is I guess. I added your other suggestions, though. Thanks! Everyone else's that I didn't comment on has been added too!
Also wow
Albacore I hate you in the nicest way possible lol. But for real, thanks for going so in-depth. I'll get to your suggestions in due time!
EDIT: Okay, here we go.
Honestly Bisharp is kind of a mess atm. have a hard time seeing Heatran as a Bisharp SSI, let alone a GSI, given that even Phys Def sets can be OHKOed by +2 LO Knock Off after SR, and Sub and WOW are both uncommon on faster sets, which take a ton from unboosted Knock Off anyway. Also if you're going to have Terrakion as an SSI, Breloom, Heracross Diancie, Lopunny, Hydreigon and all the other Dark resists that take a lot from Iron Head should be considered SSIs too (heck, all of these bar Diancie aren't OHKOed by Iron Head unlike Terrak). I also have a hard time seeing MDoom as a GSI when in the long run it's not a very good answer to Bisahrp due to the SR weakness and lack of recovery, if MDoom was my only Bisharp check I'd rethink my team personally. Also Talonflame is defenitely an SSI, bulky WoW variants take little from Knock Off due to no item and can just burn it.
Yeah, I'll move Heatran to SSI since it can still do well against some Bisharp sets, but you're right about SD. As for Terrakion, I'll probably just add it back to NSI. I've got to draw a line between SSI and NSI somewhere, and I guess that line will be losing to a threat's STABs. Agree with Talonflame and Mega Houndoom.
Personally I wouldn't put anything that can be Spored in Breloom GSIs but maybe that's just me. Also Tangrowth is defenitely an SSI if not a GSI imo.
Meh, tricky case because just about everything in the game that isn't immune to Spore fears it, so it feels weird considering that when it invalidates so many checks. I'll have to think about it, but Tangrowth is good.
Bisahrp isn't an MLatias GSI since it loses to Reflect Type, same deal for Tyranitar and MMetagross to a lesser extent.
I'll keep Tyranitar since it can still hit slam Mega Latias with Superpower even after Reflect Type. Other two have been dropped.
Latios should be added to Volcarona NSIs, Bug Buzz doesn't appear on all sets.
Latios actually fails to OHKO with Psyshock without some significant prior damage and is 2HKOed a good portion of the time by a +1 Fire Blast. Latias and her Mega are another story, though, so I think those two could fit in SSI.
Got everything else. Again, thanks for looking at this in such great detail!