Uncle, the strikes were always that way. However until last year they used to say they crit in the battle log, even though their actual damage was not changed. I think either 0.85~0.86 or Monsterbation fixed the display.
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1H level 360 Godslayer, 8168 base damage
Penetrated Armor 3 is always applied
Void Strike 11481 ~ 17221 (Heartseeker + Overwhelming Strikes + Spirit Stance)
Today my Godslayer damage is lower, so I figured out what was going on with it. Godslayer is just the normal 10% damage increase, layered multiplicatively and not additively with Demon Duality.
But yesterday was Friday. Apparently
Friday boosts all elements by 5% and this includes void damage. And probably includes your main damage and counter attacks, not just void strike. No wonder my DwD times have always been best on Friday.
Anyone doing speedruns should perform them on Friday. On the other hand be cautioned that if monsters get the same boost, you are most likely to die on Fridays.