Idea of Specially Defensive Gyarados made me quite curious, so I tested few damage calcs to see how it looks. Also created few situations to see how it works. It's not bad and in some places it's interesting ;).
MixMence 2OHKoes you with Draco Meteor no matter what when Stealth Rock is up. Without it however, Gyarados makes almost perfect Mence check (only fearing CBMence and SpecsMence). When you face DDMence, Intimidiate show it's magic - of course you die to Outrage, but -1 Outrage can't 2OHKo Porygon2, as double Intimidiate kicks in and you outsmarted opponent with this play. And Salamence user is forced to use Outrage or you just Roar him out. Or you just switch in bulky steel to easily eliminate Outraging Salamence. If you can keep SR away from battlefield, this Gyarados makes surprisngly effective Mence check. Forretress is good partner here as you absorb fire attacks aimed on it so easily and Rapid Spin is always great addition here. However, something else for Rotom-H would be nice and Tyranitar works here having good defensive synergy with you.
Gyarados also makes solid check for Gengar without Thunderbolt, as best neutral hit Gengar may dish out against you (which is Specs Shadow Ball) has only 13% chance to 2OHKO you with SR up. Substitute versions are easily dealt with, however Trick is annoyance, which don't help you.
Infernape is beaten 100% of time, if it doesn't run physical electric attack (and it's really rare) or if it doesn't run SD set. NP Mixape deals... 31% max with Nasty Plotted Grass Knot, which is quite impressive. And Close Combat with Intimidiate deals laughable damage, so yeah, you win ;).
Interesting thing is, that you still may check Lucario and now even better, as Specs Lucario can only 2OHKO with HP Rock and only if SR is up. Without it, it's impossible. +1 Close Combat deals 34.3% - 40.4%, so you may switch in and Roar it out. You loose to Stone Edge versions, but physically bulky Gyara has the same problem, so it doesn't matter.
Scizor also has similar problem, as it deals 21.6% - 25.6% with +1 Bullet Punch and you also may Roar it out, so you still deal quite well with physical attackers if you need to. The best what Scizor can do is 33.8% - 39.8% with +1 Night Slash.
Another interesting thing is that Life Orb Heatran with HP Electric deals... 73.1% - 86.3% damage, which is quite nice. Again SR is annoying, but still it's not bad. Without it you only have problems with Explosion.
Situation with Latias is interesting, as you may also check it, however Specs Draco Meteor 2OHKoes you, so it may be troublesome in some situations. Thunderbolt is also dangerous, but you may check few versions, especially when Latias like to run HP Fire to deal with Scizor. Offensive Latias with Life Orb deals 31.2% - 36.8% with Dragon Pulse, so you may Roar it out again, however you can't beat it one on one unfortunately.
Anyway, I think I'll try this set as it looks interesting on paper ;). I hope someone find this little analyses usefull and will want to also try it ;).
MixMence 2OHKoes you with Draco Meteor no matter what when Stealth Rock is up. Without it however, Gyarados makes almost perfect Mence check (only fearing CBMence and SpecsMence). When you face DDMence, Intimidiate show it's magic - of course you die to Outrage, but -1 Outrage can't 2OHKo Porygon2, as double Intimidiate kicks in and you outsmarted opponent with this play. And Salamence user is forced to use Outrage or you just Roar him out. Or you just switch in bulky steel to easily eliminate Outraging Salamence. If you can keep SR away from battlefield, this Gyarados makes surprisngly effective Mence check. Forretress is good partner here as you absorb fire attacks aimed on it so easily and Rapid Spin is always great addition here. However, something else for Rotom-H would be nice and Tyranitar works here having good defensive synergy with you.
Gyarados also makes solid check for Gengar without Thunderbolt, as best neutral hit Gengar may dish out against you (which is Specs Shadow Ball) has only 13% chance to 2OHKO you with SR up. Substitute versions are easily dealt with, however Trick is annoyance, which don't help you.
Infernape is beaten 100% of time, if it doesn't run physical electric attack (and it's really rare) or if it doesn't run SD set. NP Mixape deals... 31% max with Nasty Plotted Grass Knot, which is quite impressive. And Close Combat with Intimidiate deals laughable damage, so yeah, you win ;).
Interesting thing is, that you still may check Lucario and now even better, as Specs Lucario can only 2OHKO with HP Rock and only if SR is up. Without it, it's impossible. +1 Close Combat deals 34.3% - 40.4%, so you may switch in and Roar it out. You loose to Stone Edge versions, but physically bulky Gyara has the same problem, so it doesn't matter.
Scizor also has similar problem, as it deals 21.6% - 25.6% with +1 Bullet Punch and you also may Roar it out, so you still deal quite well with physical attackers if you need to. The best what Scizor can do is 33.8% - 39.8% with +1 Night Slash.
Another interesting thing is that Life Orb Heatran with HP Electric deals... 73.1% - 86.3% damage, which is quite nice. Again SR is annoying, but still it's not bad. Without it you only have problems with Explosion.
Situation with Latias is interesting, as you may also check it, however Specs Draco Meteor 2OHKoes you, so it may be troublesome in some situations. Thunderbolt is also dangerous, but you may check few versions, especially when Latias like to run HP Fire to deal with Scizor. Offensive Latias with Life Orb deals 31.2% - 36.8% with Dragon Pulse, so you may Roar it out again, however you can't beat it one on one unfortunately.
Anyway, I think I'll try this set as it looks interesting on paper ;). I hope someone find this little analyses usefull and will want to also try it ;).
