As this comes up quite a bit, I thought I’d share my experience using each spec. Today I ran 3 visions on my warlock, using the same gear(Roughly 444 ilvl iirc), no special corruptions, Rank 2 vision of Perfection for main essence, Azerite reforged before each run, no consumables, items, or buffs. Cloak level was 7, researched the revive and partway into chests. Let me know if you want specific breakdowns on what talents and traits I used.
First, let me preface that with each spec I was able to 3-chest it, 3 mailboxes, and get every cache I found. If you have a strong preference I don’t think it will hold you back, but there was a noticeable difference between the three. It goes without saying, but obviously YMMV.
Destruction was first, as I figured it would perform the best. It did well, very bursty. Cataclysm worked great to pull packs, and I don’t think I ever felt I was in danger of dying. I’d say probably the simplest or at least most straight-forward spec, and there’s not much more to say about it. Ended the run almost out of sanity, but still a clean clear and didn’t need to use my auto-rez.
I tried demo next. A more complicated spec, it still performed quite well, though I did have to periodically heal my FG. I put a little more emphasis on AOE than just burst, which seemed to work well. I ended up running out of sanity at one point and used the rez, but still managed to finish up though it was close.
Affliction I had used previously and felt a bit underwhelmed, but with more experience and gear it was a completely different story. A notable trait I used was the one that powers up your drain life x3, which to give you an idea was able to 1-shot one of the two NPCs in front of the Cathedral at 50 stacks. I don’t think it is necessary to have this trait much less three, but being able to periodically delete high-HP mobs or take big chunks out of bosses was very strong. On top of that, multi-dotting works incredibly well in visions so pulling pack after pack was very efficient. I made a few mistakes(fire-jumped into an extra pack, got caught by the silencing-chains from the trade district boss, etc) but still managed to finish without using my rez and more than half my sanity remaining.
Honorable mention, Burning Rush was fantastic in all three specs and helped cut down time when opening cages, setting bombs, or just running to more mobs.
TLDR:
Destruction: A
Demonology: A-
Affliction: A+