Destruction, in general, is fine. The more significant issues as I see are - baseline AoE lacking and too many single target vs multitarget talent choices, making it challenging to have the ability to effectively do both at the same time. But one thing is certain, you can pull your weight in current content as Destruction, beaten only by specs, which beat everyone equally badly at the moment.
Demonology and Affliction do need help, obviously with their hysterical ramp up time and they also have some significant baseline weaknesses like Affliction single target and Demonology flow disruption, where Affliction literally has no single target worth mentioning at all, while Demonology is really penalized by movement or various windows of no DPS/interruptions.