As we’ve seen images of runes in slots not yet materialized in P1, I’m going to have to assume that new runes will come in new slots and our current rune selection in existing slots will likely be final.
First of all I have to say that SBV is a really cool and thematic ability that feels fun to use. Splurging out shadow bolts at everything in sight feels great. There are however some really glaring problems with the rune.
Importantly, it reduces the damage of Shadow Bolt by 20% when slotted. This is fine for cleave purposes, it just nerfs the overall damage a bit, nothing surprising there, it still feels good to use. The problem is that this is a passive ability, not an active one, meaning the only way to turn it off if you want to deal single target damage is to remove the rune entirely. While having a rune that is solely useful in AOE situations is alright, making it so equipping the rune is a straight up nerf to your character if you are not hitting multiple targets feels absolutely atrocious. For example, Living Flame might be a primarily AOE spell but it doesn’t magically make you do 20% less damage if you’re hitting single target. It’s also worth nothing SBV isn’t exactly a spectacular aoe ability either as it’s cleave with a maximum amount of targets.
You might say “well just dont use shadow bolt for single target then lol” but the only time you’d be using SBV is if you’re already playing a shadow damage build, in which case your only available filler is SB. This essentially necessitates that you swap into SBV for trash and swap to something else on every single boss, which feels really bad for an ability that is otherwise fun to press. It is also only useful in an instanced setting so this is the only way to use this rune in the entire game, it’s a straight up nerf for solo content and obviously unuseable in PVP.
Shadow Bolt is also absolute garbage compared to Incinerate, doing pretty much the same amount of damage as Incinerate but in 3 seconds instead of 2.25 and for almost twice the mana cost, not to mention Incinerate gives a 25% fire damage buff for 15 seconds guaranteed which is way better than the RNG and limited charges of Improved Shadow Bolt(which also costs talent points). This is evidenced by the fact the best Affli build with +shadow damage bis gear will still use Incinerate as filler…
Then we come to the other problem, which is the spec distribution of warlock abilities. The way runes were spread out for warlock is that for every slot there is 1 rune for each of the 3 specs as well as 1 for tanking. For demonology, these are Demonic Tactics, Demonic Pact and… Shadow Bolt Volley. Destro/firelock gets Chaos Bolt, Affliction gets Haunt, Tank obviously takes Metamorphosis, but for Demonology there’s only an AOE passive that gimps your single target damage.
If you want to go hard into demonology at level 40, (fingers crossed with a Felguard rune) Haunt will be terrible as you won’t have Master Channeler nor instant corruption, Chaos Bolt feels bad as you won’t have incinerate since DP takes that slot so you will likely want to stack shadow damage and cast shadow bolt, (and CB does fire) but then the only option left is a rune that straight up nerfs you on single target fights.
Anyhow, I don’t want to extend this wall of text beyond the horizon, so this is my recommendation for the rune to make it a bit more playable:
Keep the damage reduction on the cleave, maybe increase the target limit for the volley (mages can already aoe 2000 mobs at once, it won’t break the game any more than they already do when it comes to aoe), but implement a dynamic damage modifier where if your SB only hits 1 target, it does 20% more damage instead of 20% less.
This would single handedly fix the rune being completely useless outside of instances, being 100% forced into swapping out of it outside trash, Shadow Bolt being worthless compared to Incinerate and Demo DPS not having anything to pick in that rune slot. (If demo becomes viable as a standalone spec, that is)