It makes sense for Chesnaught, Delphox and Greninja to get Megas because they debut in the same generation as said mechanic. What tier would they be in?

Mega Chesnaught
Type: Grass/Fighting
Ability: Bulletproof
Base Stats: 88/147/162/74/95/64

Mega Delphox
Type: Fire/Psychic
Ability: Magic Guard
Base Stats: 75/69/82/154/130/124
Now learns: Thunderbolt and Energy Ball

Mega Greninja
Type: Water/Dark
Ability: Protean
Base Stats: 72/140/67/148/71/132