Q: What are masterwork rolls?
A: Most legendary weapons are capable of being Masterworked. The masterwork system is a way for you to upgrade your favorite weapons to their maximum potential.
Q: What does it take to upgrade a weapon to a masterwork?
A: Upgrading your weapons, in broad terms, takes a small amount of glimmer, legendary shards, and, most importantly, Enhancement Cores.
Depending on what Tier your weapon is at, the requirements to raise it to the next tier increase the closer the weapon is to being fully masterworked (Tier 10).
Q: What benefits do I get for masterworking a weapon?
A: Each tier that you increase your weapon will grant a small buff to a single stat, chosen randomly when the item drops.
Beyond that, at Tier 5 you gain access to a kill tracker. At Tier 10, your multi-kills will generate orbs of light.
Q: So what are these "masterwork roll" stats?
A: These are the possible stats that upgrading your weapon will grant a bonus to. Depending on what tier you are at, you can grant anywhere from 1-10 additional points in any of the stats listed to your weapon.
Q: Any catch with this?
A: The Bungie API currently says that all weapons can potentially roll with all stats as their masterwork stat. This obviously isn't accurate, as Blast Radius isn't applicable to, say, Auto Rifles.
The list you see on this page is trimmed to only show stats that actually appear on the weapon. However, it is possible that Bungie has additional logic behind the scenes that further filters these
possibilities to, for example, prevent certain items from being able to have an Impact masterwork. Until Bungie modifies the API files to 100% accurately display which masterwork stats are possible on
each item, take what you see here with a pinch of salt.
So why is this exotic good for arc locks, especially for harder endgame content? As I just mentioned, there is no way you chain multikills or easily get ability kills to get amplified when enemy health bars are chunkier. With this exotic, you eat your grenade, get a stronger arc soul (which does 5 shots per burst, while the "normal" soul does 3 until you are amplified) and are amplified to benefit from the damage resist. You also get ability energy back which allows you to throw your nades, you could go flashbang for blinds in GMs or pulse with the magnitude fragment. Slot in a utility kickstart mod for that rift CD since it extends your soul, elemental charge mod (to get armor charges from ionic traces), grenade kickstart, arc surge(s), bolstering detonation and the rest to your liking. Run 100 disc, 90 resil and 80-100 recovery.
Combine with coldheart in non-GMs and with centrifuse plus catalyst in GMs for additional blinds / explosions.
Even going forward, when the artifact perks are removed, this will still be a good option for arc warlock endgame exotic.