Usually when people think "physical tank" they think Gliscor, Hippowdon, Skarmory... stuff like that. But in Platinum, new upgrades to physical sweepers like Scizor and Lucario make these pokemon pretty useless as far as physical walling goes. Here is why.
Gliscor
Defenses: 75/125/75
Useful Resistances: Fighting, Ground, Bug
Positives
-Best Heracross counter in the game
-Becomes resistant to Rock when Roosting
-STAB Earthquake helps against Tyranitar and Lucario
Negatives
-4x Ice Weakness
-Water Weakness
Hippowdon
Defenses: 108/118/72
Useful Resistances: Rock
Positives
-Toughest Physical wall in OU
-Excellent CBtar switch-in
-Good PHazer due to sturdiness
Negatives
-Weak to Water and Ice
-Vulnerable to Toxic Spikes
Skarmory
Defenses: 65/140/70
Useful Resistances: Dark, Ground, Steel, Dragon, Bug
Positives
-Excellent Spiker
-Roost makes it resistant to Rock
-Immune to Toxic
Negatives
-Does not resist Fighting
-Low damage output
Now that Swords Dance Lucario got Ice Punch, it can rip through all of these walls fairly easily. Gliscor no longer walls it, while Hippowdon and Skarmory are OHKOed after a bit of residual damage.
Scizor isn't fazed by any of their attacks, and has Roost so it can actually turn all these walls into set-up fodder. Can 2HKO them all after a Swords Dance. The only thing they can do is Roar it away.
These Pokemon are all Gyarados bait as well, with two of them being weak to Water, while Skarmory can't do anything outside of Whirlwind Gyarados.
This is where Weezing comes in.
Weezing
Defenses: 65/120/70
Useful Resistances: Fighting, Ground, Bug
Positives
-Immune to Ground and has no weakness to Rock either
-Has a diverse Special movepool to hit the Pokemon it is supposed to be walling
-Immune to Toxic
-Has but one weakness, which is not at all common coming from physical sweepers
Negatives
-Abysmal Special Defense
-Takes damage from Sandstorm
-Pain Split is useless at times
Weezing @ Leftovers
Bold
252 HP 216 Def 40 SpA
Flamethrower
Will O Wisp
Hidden Power Ground / Thunderbolt
Pain Split
Hidden Power Ground vs 4/0 Heatran: 54-63% (2HKO)
Thunderbolt vs 4/0 Gyarados: 75-88% (OHKO with SR)
Flamethrower vs 4/0 Lucario: 59-70% (2HKO)
Flamethrower vs -1 Def Lucario: 89-105% (OHKO with LO)
Flamethrower vs 252/0 Scizor: 87-102% (OHKO with SR)
Flamethrower vs 4/0 Scizor: 106-125% (OHKO)
All the following are with Adamant natures, 252 Attack, and Life Orbs.
+2 Lucario Close Combat vs Weezing: 48-57%
+2 Scizor Bullet Punch vs Weezing: 54-64%
+1 Gyarados Waterfall vs Weezing: 52-62%
As you can see from the above calculations, no matter what action these Pokemon take, they will never get the jump on Weezing. Weezing resists Fighting, and is not weak to any of Swords Dance Lucario's other moves. It has Fire attacks to leave a nice dent in Lucario, snagging a OHKO if Lucario uses Close Combat, 2HKOing if it has not launched an attack. Weezing can take hits from Gyarados too, and can retaliate with Thunderbolt. Scizor can't kill Weezing before it too meets a fiery doom.
Hidden Power Ground can be used to 2HKO Heatran, who would just love to switch in for a free Flash Fire Boost. Thunderbolt is for the aforementioned Gyarados.
Weezing's only letdown is the lack of reliable recovery. However, Pain Split isn't all that bad, and can keep him healthy enough to chase off these Pokemon several times.
As you can see, packing Weezing gives you a fairly safe answer for the top physical threats in Pokemon Platinum. The only letdown is the lack of Recovery, however, paired with a Wish Blissey, it should be fairly easy to keep around.
Gliscor
Defenses: 75/125/75
Useful Resistances: Fighting, Ground, Bug
Positives
-Best Heracross counter in the game
-Becomes resistant to Rock when Roosting
-STAB Earthquake helps against Tyranitar and Lucario
Negatives
-4x Ice Weakness
-Water Weakness
Hippowdon
Defenses: 108/118/72
Useful Resistances: Rock
Positives
-Toughest Physical wall in OU
-Excellent CBtar switch-in
-Good PHazer due to sturdiness
Negatives
-Weak to Water and Ice
-Vulnerable to Toxic Spikes
Skarmory
Defenses: 65/140/70
Useful Resistances: Dark, Ground, Steel, Dragon, Bug
Positives
-Excellent Spiker
-Roost makes it resistant to Rock
-Immune to Toxic
Negatives
-Does not resist Fighting
-Low damage output
Now that Swords Dance Lucario got Ice Punch, it can rip through all of these walls fairly easily. Gliscor no longer walls it, while Hippowdon and Skarmory are OHKOed after a bit of residual damage.
Scizor isn't fazed by any of their attacks, and has Roost so it can actually turn all these walls into set-up fodder. Can 2HKO them all after a Swords Dance. The only thing they can do is Roar it away.
These Pokemon are all Gyarados bait as well, with two of them being weak to Water, while Skarmory can't do anything outside of Whirlwind Gyarados.
This is where Weezing comes in.

Weezing
Defenses: 65/120/70
Useful Resistances: Fighting, Ground, Bug
Positives
-Immune to Ground and has no weakness to Rock either
-Has a diverse Special movepool to hit the Pokemon it is supposed to be walling
-Immune to Toxic
-Has but one weakness, which is not at all common coming from physical sweepers
Negatives
-Abysmal Special Defense
-Takes damage from Sandstorm
-Pain Split is useless at times
Weezing @ Leftovers
Bold
252 HP 216 Def 40 SpA
Flamethrower
Will O Wisp
Hidden Power Ground / Thunderbolt
Pain Split
Hidden Power Ground vs 4/0 Heatran: 54-63% (2HKO)
Thunderbolt vs 4/0 Gyarados: 75-88% (OHKO with SR)
Flamethrower vs 4/0 Lucario: 59-70% (2HKO)
Flamethrower vs -1 Def Lucario: 89-105% (OHKO with LO)
Flamethrower vs 252/0 Scizor: 87-102% (OHKO with SR)
Flamethrower vs 4/0 Scizor: 106-125% (OHKO)
All the following are with Adamant natures, 252 Attack, and Life Orbs.
+2 Lucario Close Combat vs Weezing: 48-57%
+2 Scizor Bullet Punch vs Weezing: 54-64%
+1 Gyarados Waterfall vs Weezing: 52-62%
As you can see from the above calculations, no matter what action these Pokemon take, they will never get the jump on Weezing. Weezing resists Fighting, and is not weak to any of Swords Dance Lucario's other moves. It has Fire attacks to leave a nice dent in Lucario, snagging a OHKO if Lucario uses Close Combat, 2HKOing if it has not launched an attack. Weezing can take hits from Gyarados too, and can retaliate with Thunderbolt. Scizor can't kill Weezing before it too meets a fiery doom.
Hidden Power Ground can be used to 2HKO Heatran, who would just love to switch in for a free Flash Fire Boost. Thunderbolt is for the aforementioned Gyarados.
Weezing's only letdown is the lack of reliable recovery. However, Pain Split isn't all that bad, and can keep him healthy enough to chase off these Pokemon several times.
As you can see, packing Weezing gives you a fairly safe answer for the top physical threats in Pokemon Platinum. The only letdown is the lack of Recovery, however, paired with a Wish Blissey, it should be fairly easy to keep around.