Got a few upgrades and keeping a steady 16k dps isn't a problem as destro. On a few fights I passed the 21k - but that was due to external buffs from mechanics.
I also forgot to mention destro can bring the ISB debuff in the absence of a mage. Add that to the rotation and you most definately have the most challenging spec (in game probably).
As a long time affliction player (whole duration of wotlk) I enjoy the breath of fresh air that is destruction. Demo is nice for pvp, way overpowered if you ask me, but whatever