Re: Scyther with eviolite
Brick Break/Quick Attack/Roost
Sweepy Scyther with Eviolite for bulk. Choose your boosting move of choice and attack with your dual STAB. I'd really go with Brick Break in the final slot so steels don't wall you, but priority or Roost can also work.
Bug Bite/Ariel Ace
Bulky baton pass. Use your boosting move of choice then shift it over to a team mate. Substitute blocks status and Dragon Tail and can also be passed along, while Roost increases your longevity. Finally a STAB move rounds out the set. Arial Ace is better in OU, Bug Bite is better in UU and Ubers.
You can't really go any more defensive than that BP set, Eviolite is nice and all but Scyther doesn't have the typing or stats to act as an actual tank. As said above, Scyther gets Roost through Gen 4 breeding. Since there's nothing to gain in Gen 5 breeding, get your Scyther in DPP before shipping it over.