You seem to missunderstand. If i pick a mon to stop Pinsir, i want that mon to be able to do that every time, no matter what moveset Pinsir runs. That has nothing to do with hardwalling everything. Its more about doing its job reliably and not just in some cases.
252 SpA Life Orb Latios Hidden Power Fighting vs. 252 HP / 40 SpD Ferrothorn: 146-174 (41.4 - 49.4%) -- guaranteed 3HKO
"unable to beat you" is an understatement here. Especially considering that Ferro cant do jackshit to Latios unless it runs Gyroball which doesnt have much use outside of that.
Regarding your other statements directly from the latest 1825 usage stats:
Bisharp:
Moves | | Sucker Punch 98.811% | | Knock Off 98.587% | | Iron Head 97.646% | | Swords Dance 63.545% | | Pursuit 27.406% | | Other 14.005%
So much for "runs pursuit over SD most of the time".
Tyranitar:
Moves | | Stone Edge 66.315% | | Crunch 64.338% | | Earthquake 55.369% | | Stealth Rock 46.059% | | Pursuit 38.326% | | Ice Beam 25.405% | | Dragon Dance 24.051% | | Fire Blast 23.714% | | Ice Punch 20.388% | | Superpower 11.799% | | Rock Slide 8.610% | | Other 15.625%
With Fireblast and Superpower thats a decent potion of the TTars out there that can break Ferro.
Azumarill:
Moves | | Aqua Jet 99.418% | | Play Rough 99.180% | | Waterfall 86.929% | | Belly Drum 41.953% | | Knock Off 32.977% | | Superpower 25.710% | | Other 13.834%
Got to admit, knock off is more common but Super Power still makes 25% so its not like it can be neglected. And Knock off is more for AV Sets anyway, there isnt much point to running it on CB sets as it only helps against Aegi who takes tons of damage from CB Waterfall.
Greninja
Moves | | Ice Beam 95.331% | | Hydro Pump 71.444% | | Extrasensory 65.587% | | Dark Pulse 49.271% | | U-turn 19.501% | | Surf 16.082% | | Hidden Power Grass 15.706% | | Hidden Power Fire 14.420% | | Haze 13.894% | | Scald 8.665% | | Grass Knot 6.937% | | Shadow Sneak 5.945% | | Other 17.217%
Not too common and for good reason but it fucks you up all the more when you run into it as it outright ohkos so its an amazing lure.
Huh you got me on bisharp... well then I yield on Bisharp but on the lati's you have to remember that leech seed +Protect + Lefties is 40% HP Back between the hits meaning you will get off a Gyro Ball or T-Wave without too much worry.
Some Reasons for Gyro Ball:
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 252 HP / 0 Def Mega Tyranitar: 218-258 (53.9 - 63.8%) -- guaranteed 2HKO
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Mega Pinsir: 132-156 (48.5 - 57.3%) -- 91.8% chance to 2HKO
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 252 HP / 0 Def Deoxys-S: 169-199 (55.5 - 65.4%) -- guaranteed 2HKO
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Latios: 186-219 (61.5 - 72.5%) -- guaranteed 2HKO
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Kyurem-B: 308-366 (78.5 - 93.3%) -- guaranteed 2HKO after Leftovers recovery
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Landorus: 169-199 (52.8 - 62.1%) -- guaranteed 2HKO (For a predicted Switch ONLY)
4 Atk Ferrothorn Gyro Ball (97 BP) vs. 252 HP / 0 Def Clefable: 258-306 (65.4 - 77.6%) -- guaranteed 2HKO after Leftovers recovery (Predicted Switch In)
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Garchomp: 160-190 (44.6 - 53%) -- 30.5% chance to 2HKO (Predicted Switch)
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Dragonite: 160-190 (49.3 - 58.6%) -- 98.8% chance to 2HKO (If multiscale is Broken)
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 4 HP / 0 Def Gengar: 232-274 (88.5 - 104.5%) -- 31.3% chance to OHKO (Switch In)
4 Atk Ferrothorn Gyro Ball (150 BP) vs. 0 HP / 0 Def Terrakion: 338-398 (104.6 - 123.2%) -- guaranteed OHKO (Dat Predicted Switch Tho)
Power Whip also gives viable options OHKOing Greninja, almost getting Keldeo, and almost getting Terrakion on the switch
This is an almost Uninvested (in attack) WALL Punishing Switches big time.
A list of Mons T-Wave Ruins: Zards, Deo-S, Pinsir, Keldeo, Lati@s, Terrakion, Gyarados, Greninja, Talonflame (Kinda), T-Tar (Scarf or Mega), Dragonite, Gengar.
I do get your point though on the reliability but lets face it there isn't a single Poke that hard walls all Azumarill (Ferro comes closest alongside Bulky Zard X)