I finally went ahead and tested this on my account, and I finally understand the confusion regarding how Lore of Steel functions that I have found in online posts. The description currently reads:
“Increases the Base Stat Set Bonuses of All Artifact Sets that increase Base Stats by 15%. This increase is multiplicative, not additive.”
Many people read this description to mean that Lore of Steel only modifies the Artifact Sets that Increase Base Stats by 15%, such as Life Sets, Offense Sets, Divine Offense Sets, Immortal Sets, etc. Plarium’s description is not technically wrong, but it is very clumsy phrasing. The confusion stems from the combination of (1) The Mastery grants a “15%” Artifact Set Bonus Increase, (2) Many Artifact Sets Modify Base Stats by “15%”, and (3) The Placement of “15%” in the sentence.
A much clearer way to phrase the description of Lore of Steel would be:
“Provides a 15% multiplicative increase to the Set Bonuses of all Artifact Sets that modify Base Stats.”
I have included Before & After Pics of my Frozen Banshee to show the following:
• One Accuracy Set: 40 * 15% = 6 point increase: 131 went to 137
• Two Speed Sets: 24 * 15% = 3.6 point increase: 37 went to 41