Can fragments hit the main target?
There’s Brimstone, Canister Bomb, Vile Eruption, Panetti’s Replicating Missile, Rune of Kalastor, Ravenous Earth, and Fissure (Magi).
Does the size of the opponent matter? If so, can most nemeses be hit, or are humans too small?
Yes, yes and yes. Some of these skills are easier to shotgun than others, like Fissure and Rune of Kalastor/Ignition. Canister Bomb is a bit harder to shotgun smaller foes (humas and small creatures) but works amazingly well to proc Fissure on groups of enemies. Brimstone will always have at least some shotgun going on, the larger the enemy the better, even more if you’re a Purifier and proc Storm Spread at point blank range.
Yes: canister bomb, runes, ravenous earth, fissure. These all have multiple projectiles that either have overlapping ranges (cb) or have all projectiles spawn in a single point enabling shotgun effects.
The others: not actually completely sure. My instinct says no because these are secondary effects that spawn on impact of the main target. These projectiles don’t pierce (prm excepted, maybe?) and if they hit the original target they would disappear. Experience tells me that doesn’t happen, so I assume they don’t hit the original target.
I kinda knew that some didn’t hit but I couldn’t figure out which ones, but the primary vs secondary effect thing makes sense.
I saw a post somewhere that said a PRM build shredded Mad Queen so it might just have too large a spawn radius for the fragments to hit most targets.
I noticed you said “runes”, does that mean RoH also shotguns the target? It’s not a fragment so I didn’t include it on the list, but if it does shotgun, that would explain why people say it’s a strong skill and I couldn’t figure out why. I’ve never used it in an endgame build so I don’t know from experience.
Fissure does not shotgun test dummies, which makes me think it doesn’t shotgun anything else. It’s hard to see during combat though, so I’m not sure if larger enemies get shotgunned.