Only problem isBulky SD Mega Scizor needs a revamp since Aegi's ban.
Personnaly I use the following spread : 248 HP / 100+ Atk / 116 Def / 44 SpD
Avoid 2HKO from LO Kyu-B and Adamant Excadrill, both after SR, and giving a jump point against Adamant Landorus-T (Jolly is better but Adamant is quite common). Most Heatran run some Spe EVs to avoid speed creeping fom Mega Scizor or outspeed Mega Venusaur and Suicune, so I don't think that speed creeping Heatran is useful.
252+ SpA Life Orb Teravolt Kyurem-B Earth Power vs. 248 HP / 44 SpD Mega Scizor: 126-149 (36.7 - 43.4%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Mold Breaker Excadrill Earthquake vs. 248 HP / 112 Def Mega Scizor: 127-150 (37 - 43.7%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Landorus-T Earthquake vs. 248 HP / 112 Def Mega Scizor: 135-159 (39.3 - 46.3%) -- 22.3% chance to 2HKO after Stealth Rock
252+ Atk Landorus-T Earthquake vs. 248 HP / 116 Def Mega Scizor: 133-157 (38.7 - 45.7%) -- 14.8% chance to 2HKO after Stealth Rock
232 SpA Mega Gardevoir Focus Blast vs. 248 HP / 44 SpD Mega Scizor: 148-175 (43.1 - 51%) -- 97.7% chance to 2HKO after Stealth Rock
Considering that Mega Scizor is supposed to beat MGardevoir:
232 SpA Mega Gardevoir Focus Blast vs. 248 HP / 100+ SpD Mega Scizor: 127-150 (37 - 43.7%) -- guaranteed 3HKO after Stealth Rock
So instead, run 248 HP / 44 Atk / 116 Def / 100+ SDef.