That's assuming the destro warlock is just standing still casting absolutely nothing until 4 shards are generated. You immolate, Conf, rack up stacks with double incinerate, use 1 CB, incinerate and/or conf, use your casts now with increased cast speed and if you can, time the casts as close to 0.5 seconds left on buff so you can fear and follow up with incinerate and/or conf. Comparing destro to mage/boomkin here is not really ideal, this thread is about which spec performs best for Warlock, not how much better/worse Warlock is compared to other classes. If you were to have arcane mages, boomkins, any other classes and a destro warlock in a big group battle, the destro warlock is most likely going to top total damage done when played correctly, this is what makes destro good, their padded damage is amazing in BGs, on top of that you can burst pretty well. On a geared player, with just 183 intellect and using weapon swap for power torrent, you can do over 1k damage instantly.
Playing with the mindset of a class only being viable based on what they do to one person is a really bad way to view how a class performs in a battleground as well as tournaments with all twinks. Affliction is just sustained damage on single target and their sustained damage is not even high. The only time Affliction is questionably better vs single target, is dueling. With all the cast time and missing a lot of the important abilities that makes Affliction stand out, it's just generally a weaker link in BGs and I'm willing to prove this to any warlock that plays Affliction at 19. A destro warlock is going to provide even better kill secure in comparison because of how fast shards generate when you have 4+ immolates up, even 3+ and utilizing incinerate correctly.
To be fair OP asked if lock was even good, to which I believe most people would say certainly viable but outclassed by other casters.
Also you’re referencing 19s when this is about 39s. The scaling is different and I just don’t think Destro holds up without access to big bolt. On top of that the meta in 39s is much more melee dominated (as opposed to the mostly caster meta of 19s). You just don’t get to stand there and freely cast. Most classes have their interrupts, snares and stuns by this point.
Can destro work and even be effective in the hands of a good player with a pocket healer and teammates peeling? Absolutely. Are you going to have a bad time when you solo queue? Absolutely.
Exactly why I can almost guarantee Affliction would probably be worse. Nothing changes between Affliction and Destruction at 39, you all unlock the exact same abilities besides Affl having SoC and Destro having RoF, thus, you're now in a bracket where interrupts/stuns/utilities are more dominant and more casting is required from Affliction in comparison of Destro to ramp up damage with how many times you have to cast UA. If I had a 39 destro warlock I'm 99% certain I would still outplay any Affliction warlock, the other 1% being that I wouldn't be grandfathered or have .01%/.02% BiS BoE drops.
[EDIT] Also, Arcane is still very strong at 39 bracket, you just won't see anyone that knows how to play Arcane correctly. Anyone that played Arcane the way Ziqo and Xaryu played it during Legion, is exactly how Arcane is to be played currently at low levels. This counters any twinked fury/arms warrior and all 3 rogue specs. So technically Arcane can still shut down all the meta melee, but like I said, you probably won't see that due to inexperience. I deleted my 39 arcane mage and I don't plan on playing at 39 in general because for now I'm sticking with 19 bracket and possibly 29 which I also dominate in Arcane, but I've never died to any GF'd warrior, ret pally or rogue at 39. Arcane is just too strong when the person using it knows how to play it and it's impossible for people to understand this until they see it done.
The purpose of this edited statement on Arcane, is just mainly the fact that melee is dominant at 39 and more so at other brackets simply because there are too many inexperienced players at the bracket. With how much damage Fury/Arms can do and even Ret Pally, if you have no idea how to use your CDs properly you're just going to get melted and so imo, 29/39 are both ranged dominant brackets. If you were to put r1 players or even just 2.4K - 2.6K players at 29/39 bracket, ranged DPS would be by far dominant because it's not until 40 bracket that most melee classes can deal with snares/roots/slows with pvp talents. All you can do is hope your teammates know how to play their class. Besides that, yes, it's low level PvP and there are going to be a lot of newbs, but no matter how inexperienced and how many inexperienced players there are, ranged is still dominant by fact.
I invite you to join us and roll a 39 Destro Lock to see for yourself then. I’ll even pocket heal you : P
I appreciate your insight to the 19s meta as I think destro would be pretty fun there, but it’s not as simple as adding 20 levels and saying all things are equal.
Yikes
Look, do you like playing warlock? Do you think the idea of a twink warlock sounds fun? Then you can make it work.
Sure, 39s is a burst heavy, melee dominated bracket, so the idea of playing a dot based caster seems counter intuitive, so adjust playstyle and expectations accordingly.
There's always classes that look like they under perform and there's always players who take those classes and make them seem broken
And if there's anything this bracket needs, it's people willing to roll those classes and take that chance