Hey
Remember distinctively how Shadow Bolt was the go-to in single-target/raid content in the pre-patch and the first couple of weeks after Nerubar Palace opened up. Was surprised to see that it changed drastically and the vast majority of Affliction Warlock players run Drain Soul in all content over Shadow Bolt.
What happened here? Don’t remember seeing any balance change / tuning on either spell in the hotfixes Blizzard released so far. My uneducated guess would be that it’s the execute (100% increased damage vs targets below 20% HP) of Drain Soul that gives its an edge over Shadow Bolt in a raid-environment & the shard simp in Mythic+. A bit baffled here, maybe you guys can clarify this matter to me 
I mainly use Drain Soul over Shadow Bolt because it’s easier to use in-between keeping everything else up, easier to keep the stacks up and basically allows more freedom of movement. Shadow Bolt requires you to stand still for the whole cast, whereas Drain Soul refreshes the stacks pretty quickly, you only need to stand still once for a full cast to get it to 4.
That’s why I choose it anywas.
Totally cool with personal preferences like that.
Just can’t quite wrap my head around how about a month ago, the top 200 heroic logs on any given boss had like 195~ running shadow bolt while the recent logs on both mythic up to rasha’nan and all of heroic (from 24 September onwards it seems, might’ve been earlier) have ~195/200 people running drain soul over shadow bolt.
People use shadowbolt for hellcaller in st because on average it’s stronger but soul harvester has constant nightfall procs and buffs soul drain so it sims better
Drain soul when mobs die faster, such as mythic + as it gives you soul shard if it’s active when mob dies so you can basically stay at near max soul shards.
I tend to run drain soul in raid as wel, as someone has already said with the new mechanics seem to be keep moving… it allows me to move more. Shadow bolt you’ll lose dps if you stop the cast, drain soul you’ll still lose dps if you stop cast, just not as much.
People use Shadowbolt for mobility in raid.
If i have to run a lot i Prefer Shadow Bolt, if i can just stand still and DPS Soul Drain is better