I don't think any knowledgable players ever said destro was bad in our current build. It's certainly viable. That said, it's not nearly as good as aff dps-wise. As you're doing 14k dps now in icc with the 30% buff, I was doing that as aff with the 5% buff and I do rougly 20k dps now at 30%.
Gear might be an issue though.
It's very possible that some specs/classes might be overpowered come patch 4.x. As Blizzard said, these numbers are balanced around level 85.