Multistrike - Infernal Blow interaction

Currently when supporting infernal blow with multistrike this is shown as a net DPS gain, both when selecting the melee hit as well as the debuff - 6 stacks.

I believe PoB calculates the damage as if each multistrike repeat applies the debuff. However from my personal testing as well as anecdotal evidence from other people this does not appear to be the case (e.g. https://www.pathofexile.com/forum/view-thread/3191503 ).

Infact - if my calculations are correct! - I believe multistrike is a net DPS loss when it supports infernal blow. Please verify yourselves, I cannot guarantee perfect math nor a perfect understanding of the game mechanics.

If we assume a 20/0 infernal blow with the following numbers:

Base damage; 100
Attack rate: 5.0
Debuff damage multiplier: 0.66 (66%)

The DPS would be: (5 * 100) + (5 * (100 * .66) = 830
This consists of 500 melee hit and 330 debuff damage.

If we now support it with a 20/0 multistrike, which has:

Repeats: 2
More attack speed multiplier: 1.44 (44% more)
Less attack damage multiplier: 0.8 (20% less) 
Which means the base damage of the skill becomes: 100 * 0.8 = 80
First repeat more attack damage multiplier: 1.22 (22% more)
Second repeat more attack damage multiplier: 1.44 (44% more)

The attack rate would become: 5.0 * 1.44 = 7.2

However, to get the actual 'attack' rate (uses of multistrike / not counting repeats): 
To get the time in seconds it takes to do one full multistrike (attack + repeats): (1/7.2)*3 = 0.416667 (to clarify: 1 second divided by the attack rate which is then multiplied by the attack + 2 repeats)
Which means that a total of approximately 2.4 'multistrikes per second' can be done: 1/0,416667 =~ 2.4

Knowing this and assuming the debuff is only applied on the attack and not on the two repeats that follows:

Melee hit DPS (damage from attack + damage from repeat 1 + damage from repeat 2) * multistrikes per second:
 ( 80 + (80 * 1.22) + (80 * 1.44) ) * 2.4 = 702.72

The debuff DPS would be: (damage from attack * debuff damage multiplier) * multistrikes per second:
(80 * 0.66) * 2.4 = 126.72

Bringing the total DPS to 702.72 + 126.72 = 829.44

No files or tests are named. Start by reproducing the Infernal Blow and Multistrike DPS calculation described in the issue, then compare the modeled debuff application with the reported in-game behavior and linked evidence. Done means the planner's melee and debuff DPS reflect the verified interaction.