I don't think M-Scept is a D-ranked..I mean, it's a really good Special sweeper. Not much people use it, but if they did, the people would know how strong it is. This is my set:
Sceptile-Mega (F) @ Wise Glasses
Ability: Contrary
Shiny: Yes
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Overheat
-...