This is a set that I've created as an alternate way to break down premier walls such as Blissey, Dusknoir, and Cresselia.
Here below is the set and calculations that I have made in order to provide a basis for discussion.
Skuntank@ Leftovers
Ability: Aftermath
Adamant Nature
228 HP / 252 Atk / 28 Spd
- Substitute
- Screech
- Pursuit
- Rock Smash
SubScreecher. HP EVs give him 404 HP to make 101 subs. Subs against Blissey so she can't TWave me, then Screech to cut her Def in half. Pursuit will hit really hard as she tries to switch to due to Screech. Rock Smash for steels.
Pursuit vs Max HP/Def Bold Blissey (switching put after Screech)
Defender HP: 714
Damage: 418 - 491
Damage: 58.54% - 68.77%
Pursuit vs Max HP/Def Relaxed Uxie (switching out after Screech)
Defender HP: 354
Damage: 282 - 332
Damage: 79.66% - 93.79%
Rock Smash vs Tyraniboah (after Screech)
Defender HP: 404
Damage: 286 - 337
Damage: 70.79% - 83.42%
Pursuit vs Max HP/Def Bold Cresselia (switching out after Screech)
Defender HP: 444
Damage: 299 - 351
Damage: 67.34% - 79.05%
Pursuit vs 36 HP Timid Azelf (not switching and no Screech)
Defender HP: 300
Damage: 157 - 185
Damage: 52.33% - 61.67%
Pursuit vs 36 HP Timid Azelf (switching out after Screech)
Defender HP: 300
Damage: 620 - 729
Damage: 206.67% - 243.00%
Pursuit vs 180 SDef/76 Def Careful Dusknoir (switching out after Screech)
Defender HP: 294
Damage: 340 - 400
Damage: 115.65% - 136.05%
Pursuit vs Max HP/Def Impish Gliscor
Defender HP: 354
Damage: 145 - 171
Damage: 40.96% - 48.31%
Rock Smash vs Max HP/Def Impish Skarmory (after Screech)
Defender HP: 334
Damage: 45 - 53
Damage: 13.47% - 15.87%
Rock Smash vs 6 HP Heatran (after Screech)
Defender HP: 324
Damage: 148 - 174
Damage: 45.68% - 53.70%
Rock Smash vs 204 HP Metagross
Defender HP: 352
Damage: 32 - 38
Damage: 9.09% - 10.80%
Rock Smash vs 108 HP/252 Def Machamp (after Screech)
Defender HP: 348
Damage: 71 - 83
Damage: 20.40% - 23.85%
Pursuit vs 212 HP/180 Def Gyarados (switching out after Screech w/Intimidate)
Defender HP: 384
Damage: 117 - 138
Damage: 30.47% - 35.94%
Pursuit vs 212 HP/ 180 Def Gyarados (switching out after Screech w/o Intimidate)
Defender HP: 384
Damage: 230 - 270
Damage: 59.90% - 70.31%
Rock Smash vs 252HP/Def Impish Hippowdon (after Screech)
Defender HP: 420
Damage: 50 - 59
Damage: 11.90% - 14.05%
Pursuit vs Max HP/Def Hippowdon (switching out after Screech)
Defender HP: 420
Damage: 151 - 177
Damage: 35.95% - 42.14%
Rock Smash vs 252 HP Lucario (after Screech)
Defender HP: 344
Damage: 207 - 243
Damage: 60.17% - 70.64%
Rock Smash vs 6 HP Garchomp (after Screech)
Defender HP: 358
Damage: 81 - 95
Damage: 22.63% - 26.54%
Pursuit vs 6 HP Garchomp (switching out after Screech)
Defender HP: 358
Damage: 242 - 285
Damage: 67.60% - 79.61%
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Damage Calcs for attacks used against Skuntank
Dusknoir's ThunderPunch vs Skuntank
Defender HP: 404
Damage: 76 - 89
Damage: 18.81% - 22.03%
Cresselia's Ice Beam vs Skuntank
Defender HP: 404
Damage: 82 - 96
Damage: 20.30% - 23.76%
Uxie's Thunderbolt vs Skuntank
Defender HP: 404
Damage: 82 - 96
Damage: 20.30% - 23.76%
Azelf's LO Flamthrower (unboosted) vs Skuntank
Defender HP: 404
Damage: 197 - 232
Damage: 48.76% - 57.43%
Azelf's LO Flamethrower (boosted) vs Skuntank
Defender HP: 404
Damage: 392 - 461
Damage: 97.03% - 114.11%
Tyraniboah's Ice Beam vs Skuntank
Defender HP: 404
Damage: 130 - 154
Damage: 32.18% - 38.12%
Tyraniboah's Focus Punch vs Skuntank
Defender HP: 404
Damage: 193 - 227
Damage: 47.77% - 56.19%
Here below is the set and calculations that I have made in order to provide a basis for discussion.

Skuntank@ Leftovers
Ability: Aftermath
Adamant Nature
228 HP / 252 Atk / 28 Spd
- Substitute
- Screech
- Pursuit
- Rock Smash
SubScreecher. HP EVs give him 404 HP to make 101 subs. Subs against Blissey so she can't TWave me, then Screech to cut her Def in half. Pursuit will hit really hard as she tries to switch to due to Screech. Rock Smash for steels.
Pursuit vs Max HP/Def Bold Blissey (switching put after Screech)
Defender HP: 714
Damage: 418 - 491
Damage: 58.54% - 68.77%
Pursuit vs Max HP/Def Relaxed Uxie (switching out after Screech)
Defender HP: 354
Damage: 282 - 332
Damage: 79.66% - 93.79%
Rock Smash vs Tyraniboah (after Screech)
Defender HP: 404
Damage: 286 - 337
Damage: 70.79% - 83.42%
Pursuit vs Max HP/Def Bold Cresselia (switching out after Screech)
Defender HP: 444
Damage: 299 - 351
Damage: 67.34% - 79.05%
Pursuit vs 36 HP Timid Azelf (not switching and no Screech)
Defender HP: 300
Damage: 157 - 185
Damage: 52.33% - 61.67%
Pursuit vs 36 HP Timid Azelf (switching out after Screech)
Defender HP: 300
Damage: 620 - 729
Damage: 206.67% - 243.00%
Pursuit vs 180 SDef/76 Def Careful Dusknoir (switching out after Screech)
Defender HP: 294
Damage: 340 - 400
Damage: 115.65% - 136.05%
Pursuit vs Max HP/Def Impish Gliscor
Defender HP: 354
Damage: 145 - 171
Damage: 40.96% - 48.31%
Rock Smash vs Max HP/Def Impish Skarmory (after Screech)
Defender HP: 334
Damage: 45 - 53
Damage: 13.47% - 15.87%
Rock Smash vs 6 HP Heatran (after Screech)
Defender HP: 324
Damage: 148 - 174
Damage: 45.68% - 53.70%
Rock Smash vs 204 HP Metagross
Defender HP: 352
Damage: 32 - 38
Damage: 9.09% - 10.80%
Rock Smash vs 108 HP/252 Def Machamp (after Screech)
Defender HP: 348
Damage: 71 - 83
Damage: 20.40% - 23.85%
Pursuit vs 212 HP/180 Def Gyarados (switching out after Screech w/Intimidate)
Defender HP: 384
Damage: 117 - 138
Damage: 30.47% - 35.94%
Pursuit vs 212 HP/ 180 Def Gyarados (switching out after Screech w/o Intimidate)
Defender HP: 384
Damage: 230 - 270
Damage: 59.90% - 70.31%
Rock Smash vs 252HP/Def Impish Hippowdon (after Screech)
Defender HP: 420
Damage: 50 - 59
Damage: 11.90% - 14.05%
Pursuit vs Max HP/Def Hippowdon (switching out after Screech)
Defender HP: 420
Damage: 151 - 177
Damage: 35.95% - 42.14%
Rock Smash vs 252 HP Lucario (after Screech)
Defender HP: 344
Damage: 207 - 243
Damage: 60.17% - 70.64%
Rock Smash vs 6 HP Garchomp (after Screech)
Defender HP: 358
Damage: 81 - 95
Damage: 22.63% - 26.54%
Pursuit vs 6 HP Garchomp (switching out after Screech)
Defender HP: 358
Damage: 242 - 285
Damage: 67.60% - 79.61%
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Damage Calcs for attacks used against Skuntank
Dusknoir's ThunderPunch vs Skuntank
Defender HP: 404
Damage: 76 - 89
Damage: 18.81% - 22.03%
Cresselia's Ice Beam vs Skuntank
Defender HP: 404
Damage: 82 - 96
Damage: 20.30% - 23.76%
Uxie's Thunderbolt vs Skuntank
Defender HP: 404
Damage: 82 - 96
Damage: 20.30% - 23.76%
Azelf's LO Flamthrower (unboosted) vs Skuntank
Defender HP: 404
Damage: 197 - 232
Damage: 48.76% - 57.43%
Azelf's LO Flamethrower (boosted) vs Skuntank
Defender HP: 404
Damage: 392 - 461
Damage: 97.03% - 114.11%
Tyraniboah's Ice Beam vs Skuntank
Defender HP: 404
Damage: 130 - 154
Damage: 32.18% - 38.12%
Tyraniboah's Focus Punch vs Skuntank
Defender HP: 404
Damage: 193 - 227
Damage: 47.77% - 56.19%