Okay, so I decided to compare the Physical Attack of one of my Knight Emperors with one of my Immortals (both Master Class with all relevant passives unlocked). After removing all external attack power influences, I found that my Knight Emperor had 2,086 Physical Attack and my Immortal had 2,137 Physical Attack. At first I thought this made sense because of what the template said were the class multipliers, but then I realized that Immortal gets 5% more permanent Physical Attack (Additive) from his Passives than Knight Emperor. I don't know whether Awakened One or the Artifact Stage 1 Passive are additive or multiplicative, but when I tried to figure out what their base attacks before their Passives were under all assumptions, I actually ended up with higher results for Knight Emperor every time.
Also, when I tried the formula listed for the attack stats, I got a result way higher than my Immortal's 2,137 before even attempting to apply increases from Passives.