What kind of qr skewer are you using? If it's one of the boutique exterrnal cam types, it won't generate enough force to keep the wheel from slipping. Get a Shimano or Campy-type internal cam skewer with steel faces and the problem should go away. Keeping the dropout faces clean and free of oil and roughing them up will also help. The chain tensioner should be ok but should not be needed.

BTW, if the skewer force is binding the wheel, you have the bearings adjusted too tight. There should be a bit of play in the axle when the wheel is out of the bike and the play should disappear when the wheel is clamped in the dropout with the skewer.