Right now, Destro lock is kinda underwhelming. So here’s my idea on an overhaul that might prove to be more fun than how it is now?
First the Resource - No more Soul shards. Soul shards are great for Afflic, and Demo, but Destro it feels…off. I think a resource pool like Rage or Maelstrom would be great! But with a twist. Combine an eclipse pool, and a rage pool together. What do you get? Fel Energy! Or something cool like that, idk placeholder name. Now how i was thinking, is that Destro locks start baseline using fel fire (Green Fire). Yes I know, people will be mad because they worked hard to unlock it, but let’s be real, the quest chain to get that is a joke now, so it’s not even really unique. ANYWAYS, the pool levels out at 60 out of combat, and goes up to 100/200. How this works is that Chaos Bolt and such will take a certain amount of this energy, 40 if you stick with the ⅖ shard thing. So you can build up this energy with the Incinerate, and other ways that i’ll explain in a bit, and then shoot off the big abilities like normal. NOW, this does seem just like Soul Shards, because it kinda is, BUT there’s a catch. The reason why I said the pool goes up to 100/200 is because it can go beyond 100. Realistically it can go up to 200. The thing is though, once you hit 100 you start to get a buff. You are succumbing to the fel power building up inside of you, so it allows you to get even more energy quicker, and you do a little more damage. You might know where i’m going with this. At a point it starts to kill you. Holding all that power starts to burn away at your own form, slowly killing you and getting progressively worse if you don’t spend your resource. Now it will be hard and time worthy to cast a crap ton of Chaos bolts so there will be a new ability that you can only cast at 120+. Basically you erupt all the power out of you and basically do an eye beam thing but out of your hands, burning anything in a cone in massive damage, and dot damage. That doesn’t need to be the big ability, but that’s what I thought of. So to sum up, no more soul shards, and the new resource that works how i mentioned. Maybe it doesn’t need to work like that but, Idk. Would be cool to see some people risk their own life to do a crap ton of damage. Also wouldn’t it be cool to be engulfed in fel fire? B)
Ways to get Energy - Okay so basically the ways to get energy are the same as how it is now. Immolate has a chance to give some when the DOT ticks, Incinerate gives some Conflag gives some. It’s the usual. But a change i think would be really cool is making the pets give some as a passive way to get energy. When they attack you can get some or something. Right now this seems like it can be OP, but if balanced right it will be fine. Talents can be mixed around and changed so that there’s maybe procs. Like for example casting Incinerate has a chance to grant you an empowered Chaos Bolt that does less damage than a normal chaos bolt, (But better than Incinerate) have a reduced cast time, and grant * energy.
Big Boy Spec - Okay, here’s my last thing. Destro needs a Demon. What i mean by that is, Destro needs to summon Infernal as a Permanent pet. Now this will make people think that it’ll make the imp obsolete, but it really wont. Imp will cast faster, granting you more energy, but will do single target damage. Infernal will attack slower, but can hit multiple targets. Now, this might be too far of a change. But this opens up to have a bigger, more badass Infernal as our big CD. I mean like an armored one, one that will strike fear into the hearts of the Gnomes. Anyways, this is my idea. It might be bad, i don’t know… IT might seem OP, or boring. I don’t know. I just started typing. 
EDIT: So I also know that some people prefer the normal fire over the fel stuff, so easy fix! Basically a Warlock Combat “Stance”. Normal fire gives more resource but less damage, and Fel does more damage but less resource. <-- Again, doesn’t need to be this, but ideas.