I’m torn between a priest, and a warlock
I have both decently geared 437 lock, and 432 priest
I love them both, and love running mythics with both, but I just can’t decide on a main
Help me! 
Ps, if I play lock it’ll be demo, and priest will be shadow (I don’t like healing)
Locks are the lowest repped class in M+. If that’s what you enjoy, just play what you like. If you are looking to get serious at all though, locks are dead last. Mostly the lack of a kick for demo. Not that you… can’t push a lock to a decent rating, but it just make it an uphill battle.
Play what you enjoy, but it’s worth noting the following:
If you think you might want to chase a high rio rating, locks are the least favored class in m+. This is very known. They’re so uncommon that most people have absolutely no idea what real utility they bring, myself included. I don’t even know what to say about them.
Shadow priests will probably be terrible in lower keys, as their damage has ramp up time. In low keys, mobs are dead before the priest can really get going. While you said you have no interest in healing, I said that before too, and now I’m healing +18s. It grows on you, and as a priest you’ll have that option available.
Ultimately, I’d say use a priest, but if you really prefer warlock style then use that instead.
Thanks for the input guys!
I just ran some mythics with each class to get a kind of refresher.
I’m leaning towards priest. I ran an 11 shrine with the warlock, and the lack of a kick was definitely noticeable. Got one of the adds on last boss to 1% and no one had a kick up, so he went back to 100%. Made me feel like I was dragging the group down by bringing a warlock. Even swapping to fel hunter makes me a detriment to the group because my dps plummets…
Sometimes I think blizzard is punishing warlocks for affliction being such a monster in legion 
Just my personal philosophy but I always choose a toon who can fulfill multiple roles. If I had to play DPS constantly I’d be bored out of my mind.
Yeah, I’ve mained Lock and Hunter in prior expansions, and while I did really enjoy them, it felt bad not being able to do different roles.
Warlock is my Raid toon (4/8M) and prot pal is my m+ toon (1745). I can’t say I recommend lock for keys even with the few gate skips and endless pet utility (demo excluded). I mained lock in Legion for dungeons, but it’s just not in a healthy spot with the new dungeon designs.
Neither choice is great for most BFA affix + dungeon combos but if those are the two choices I would go shadow.
I just want to point out that spriest pumps a lot of damage in m+ but chances are most groups won’t know how to pull for you. The chorus of insanity trait is a massive damage steroid but it falls off completely unless the tank is chain pulling nonstop.
With that said, it’s easy to have your damage gimped and there’s not much you can do about it. And most low io tanks, especially the ones you pug won’t understand the reason why. They’ll just see the low numbers and assume it’s your fault.
Demo lock is a lot worse for m+ but it’s easier to pug through compared to a spriest. The only thing the tank has to do is keep the trash pack relatively in place. There’s no other special interaction they need to do for your damage to show up.
Shadow can do fine in lower keys with a Searing Dialogue + Thought Harvester build.
Chorus of Insanity is stronger for high keys because it pumps DPS for any number of mobs (big pulls, small pulls, bosses), while Mind Sear is only really strong on moderate-to-heavy AOE. But if you’re doing low keys or if you can’t chain-pull for any reason, then it skips the ramp-up and gives you the on-demand damage you need.
I just curious whether destruction warlock had a place in mythic +, because i once run with a warlock with destruction doing some sick aoe damage on mob pack.
About affliction though, i rarely meet affliction doing good damage in mythic.
Destro is a bit meh. All Warlocks have decent utility and tankiness (not top tier like Rogue or Boomkin, but better than Shadow for sure). Destro damage is okay - but it’s extremely reliant on the Infernal and that’s not good for M+. You can pump insane DPS for one pull and then you’re dead weight for a few mins.
If you specifically plan for certain big pulls (eg. do a huge triple pull at the start with hero) then Destro is good. But in a typical PUG where you just pull one-by-one, it’s not gonna perform well.
With that said, it’s not like the other two specs are any better for M+ at the moment. Affliction AOE damage is absolute garbage, while Demo has solid all-round DPS but no interrupt.
How Blizzard put out a class without an interrupt while simultaneously over-engineering the living hell out of trash in M+ is beyond me.
Yea, it’s frustrating. Kicks are way more important now than they were in legion. Especially in Shrine and Temple.
Because the encounter design team (M+, raiding, etc.) has little if any communication with the class/spec design team anymore.
How else could something like the mobile damage aura exist for sisters in waycrest or the ooze room in KR if so many specs are gimped in such an environment ?