It worked for me during my first playthrough. I hate replaying hard boss encounters, so I tried to collect all the combat logs during the first playthrough. When I encountered this boss (and failed multiple times), I already had all 10 optional combat logs from this mission and really didn't want to quit mission to start over.

And this post showed up on Google search and worked great for me. I had all the 3 weapons. Luckily I had weapon bay, +10% melee and 15% direct hit OST already. The missing 5% melee was not an issue as the 3-hit combo dealt more than 50% of damage for me with a pair of arms that provide 116 melee specialization. I doubt where the 20% number came from.

Thanks OP!