Why it procs the way it does in the attached video? Apparently, it does make a difference to the damage I apply while strafing.
I read the entire discussion Is Calmity Worth Running? And I understand why the damage from the rune Grim Reaper is inconsistent, but I can see that MfD procs, and in my case, increases my damage.
Would someone care to explain what I am seeing? 
The MfD from Calamity applies to one target at a time and on application you donât get the damage buff from MfD.
Say you fire your Hungering Arrow and hit a mob with it. The MfD is applied but thatâs all that happens. Now the arrow pierces and hits another mob, itâs applied the MfD but again, thatâs all that happens.
Now the arrow pierces again and hits a third mob, again, the MfD is applied but no damage because the damage from MfD only applies to a second hit to one itâs applied to.
So now the arrow pierces again and hits one of the ones that has MfD applied to it (this is the part Iâm unsure about) when the arrow hits it, it gets the extra damage but no matter what it hits after will not receive that damage. (I think, it could even be worse than that.)
Point is, MfD from Calamity is a glorified graphic that deals next to no damage because it doesnât deal the damage more than once, or something along those lines.
In higher grift, where monster need more arrows to die, should Calamity not work then? First wave of arrows applies MfD and the next waves so the damage with MfD includedâŚ
It only deals the damage once in the best case. And what I meant by it could be worse is every successive hit could just re-apply the MfD and actually deal 0 additional damage because the damage doesnât come on application.
And that second one is what Iâm thinking is actually the case. Thereâs a post explaining how Calamity was broken several patches back. I think the gist of it is, it applies the MfD but you donât get damage because the application means it cannot deal the damage.
The point with calamity is, that MfD is applied after the hit. If you fight more than one enemy at once, the most likely scenario is like that:
However, if you use MfD skilled with Valley of Death, it can work with GoD
The question remains, whether its worth it. The MfD damage bonus is additive with skill damage and Taeguk, so its only ~8% or something like that. You may try BotT instead in this setup.
And of course you have to use MfD in the skill bar for that, where you could use a different skill better.
But the way you use your Primal Calamity in your video is âvalidâ. If it works for you, do it!
Edit: For the RG, Calamity works quite well - every hit after the first one will benefit from MfD (if the boss spawns no minions, but even then it should give some bonus).
I can see your point, though it would be nice to have reliable data to prove youâre correct.
I believe youâre right. If we are fighting a single target, the weapon probably does more damage because itâs hitting with the previously applied MfD and reapplying the skill, otherwise, it wouldnât even make sense for the weapon to have that power.
I see. For what I experienced, the xbow really is doing more damage, but I could use a better item. Itâs a shame that such a beautiful weapon is so worthless. Itâs just eye candy, like @Idolis said.
If the 15% additive damage was changed to ~15%-30% multiplicative damage, on the base skill, Calamity would be probably just fine. That means itâs worth 30% more damage to you and everyone else, for âfreeâ.
This thread has some more discussion: Is Calmity Worth Running?. Also see this video.
