I completely disagree with this Klang is a fantastic and to get this out of the way the comparisons to SD Monferno an DD Fraxure are ridiculous due to the massive differences in typing and use overall.I would also like to make a nomination for Klang to C Rank.
It is very outclassed in this meta right now. With its only viable physical moves being its STAB, Return, and Wild Charge, its movepool is extremely shallow. While it does have decent stats, Shift Gear only boosts attack by one stage, so even if it somehow manages to force something out, it is still pretty weak. Having Klang set up to the point where it becomes threatening requires so many free turns. Even with decent bulk with 60/95/85 defenses augmented by Eviolite, it is still destroyed by common mons in this meta, such as Machoke, Golem, Stoutland, Stunfisk, Pawniard, Arbok, Crustle, Gourgeist-XL, and Floatzel and Rotom-F if they Trick/Switcheroo it a choice item. It is also outclassed as a bulky Eviolite steel type by Metang, who has similar bulk and useful support moves such as Stealth Rock and Pursuit. It is also
outclassed as a set-up sweeper by mons such as SD Monferno and DDance Fraxure, who have better abilities, movepools, and Attack. Overall, Klang is extremely outclassed and is just too bad for B-Rank.
252+ Atk Machoke Close Combat vs. 252 HP / 156+ Def Eviolite Klang: 194-230 (59.8 - 70.9%) -- guaranteed 2HKO
252+ Atk Golem Earthquake vs. 252 HP / 156+ Def Eviolite Klang: 186-218 (57.4 - 67.2%) -- guaranteed 2HKO
252+ Atk Choice Band Stoutland Superpower vs. 252 HP / 156+ Def Eviolite Klang: 208-246 (64.1 - 75.9%) -- guaranteed 2HKO
0 SpA Stunfisk Earth Power vs. 252 HP / 100 SpD Eviolite Klang: 114-134 (35.1 - 41.3%) -- guaranteed 3HKO
+2 0 Atk Klang Gear Grind (2 hits) vs. 252 HP / 252+ Def Stunfisk: 72-86 (17 - 20.3%)
+2 0 Atk Klang Gear Grind (2 hits) vs. 252 HP / 252+ Def Gourgeist-Super: 114-134 (30.4 - 35.8%) -- guaranteed 4HKO after Leftovers recovery
Going by the standard set Klang doesn't even use Return or Wild Charge opting for a bulky win-con set with Shift Gear,Gear Grind,Rest,Sleep Talk with its bulk,typing and access to the mentioned eviolite with a spread of 252 HP / 156 Def / 100 SpD Klang is used purely for its defensive prowess and the ability to set-up on multiple pokemon (one of which you actually mention in your "destroyed" list) a pure steel typing is beautiful in PU and allows Klang to support a team by resisting a plethora of offensive types as well as tanking certain neutral hits decently such as Water and Electric types.It is very outclassed in this meta right now. With its only viable physical moves being its STAB, Return, and Wild Charge, its movepool is extremely shallow. While it does have decent stats, Shift Gear only boosts attack by one stage, so even if it somehow manages to force something out, it is still pretty weak. Having Klang set up to the point where it becomes threatening requires so many free turns
Some of the pokemon you mentioned actually just lose to Klang such as Arbok,Crustle,Rotom-F and Floatzel all either losing or struggling in 1v1 situations, Stoutland is forced to not spam Frustration and if it does is used as set-up fodder (those locked into superpower also are set-up on at -1 attack) Gourgeist-XL doesnt even beat it with Foul Play and eventually just loses once Klang sets up to +4/5.Even with decent bulk with 60/95/85 defenses augmented by Eviolite, it is still destroyed by common mons in this meta, such as Machoke, Golem, Stoutland, Stunfisk, Pawniard, Arbok, Crustle, Gourgeist-XL, and Floatzel and Rotom-F if they Trick/Switcheroo it a choice item.
Again no, While yes both are fat steels there roles are completely different with both working in a similar placement but for different teams with Klang filling a valuable niche for rockers that dont have the coveted normal resistance like Gabite and PrinplupIt is also outclassed as a bulky Eviolite steel type by Metang, who has similar bulk and useful support moves such as Stealth Rock and Pursuit.
If anything Klang is one of the most severely underrated steel types in PU with one of the lowest usages despite its ranking (B rank) im not sure if this is due to issues with splashability or appeal however with recent touch of this mon i have to give credit were it is due with its role compression and sweeping capabilities being very effective in this meta.