We think Destro may be a little behind, but it's not much. Affliction PvE damage is too high, which causes many warlocks to go Affliction on every fight rather than considering options. That creates a big sampling bias effect on sites like World of Logs and Raidbots. The lower performing DPS specs appear even lower than they actually are because the only players generating those logs are uninformed (which also tends to mean undergeared) or just messing around. To get a more accurate test, you need to see a player try every spec under similar circumstances (gear, skill, etc.), and those data are much more rare.