Without getting too much into whether to they're fun or not, easy or not, or if their damage is weak or not, it seems like a lot of Warlocks feel that Destruction leaves a little bit of something to be desired. I think what it needs is a little bit of unpredictability.
While there's a tiny bit of unpredictability with criticals generating extra Burning Embers, Destruction follows a pretty rigid playstyle. Refresh Immolate once ever 15 seconds, cast Conflagrate on cooldown, and spam Incinerate until you have a Burning Ember to blow on Chaos Bolt or Shadowburn.
Elemental Shaman and Balance Druids have a random chance to instantly reset the cooldowns of Lava Burst or Starsurge (respectively) and causes them to be instant cast.
What I am about to propose will speed up Destruction's gameplay by greatly increasing Burning ember generation, spread the importance of Destruction's various spells out a little bit more evenly, and mix up the rotation to make it more engaging.
I think Destruction could use something like that for Conflagrate, and it's proc should be tied to Immolate.
Whenever Immolate deals damage, there is a chance to reset the cooldown of Conflagrate. If there are already two charges of Conflagrate available, the Warlock gains a third charge. Likewise, Backdraft can have up to 9 stacks.
Immolate, as it stands, is only useful because it deals more damage than one Incinerate (but not more than two), and if the stars align, possibly generating more Burning Embers than a single Incinerate. And while I feel that Conflagrate's damage is still a little too low in the grand scheme of things (but hey, at least it hits harder than Incinerate now!), it's at least pretty important to the rotation because of how powerful Backdraft is.
If by some chance these changes were to happen, Conflagrate will account for a decent bit more of the Destruction Warlock's overall damage. And while Immolate's damage will still be a fairly insignificant portion of Destruction's damage, it will at least become a more important spell to cast.
These changes could potentially make Destruction a little too strong (even though they are in need of a damage buff), so some of the damage from Chaos Bolt can be shaved off to make up for it.
These changes would make me play Destruction in a heartbeat.
What are your opinions?
It would also be nice to have Chaos Bolt's cast time lowered to, say, 2 seconds, but honestly, 2.5 isn't a deal breaker for me. And I would also love to see Corruption return to the rotation, I can appreciate that the developers want Destruction to be fire-centric and rely heavily on Nukes rather than DoTs.