[Gameplay] Deathfire Touch not working with Darius

I decided to try using deathfire touch on Darius in a custom game against a friend to see if it works. I presumed it would work with Darius's bleed passive but to my surprised it doesn't. I wonder why this is? I mean if Malzahar'z malefic vision can work with deathfire touch, Casseopia's poison works with it, and Brand's passive does so why can't Darius's bleed work with it? I also decided to do one more test and that was to see if when you stack up Darius's passive does the bonus AD apply to deathfire touch and surprise surprise it doesn't. Granted I did do this on the PBE but I believe this would also apply on the live servers as well.

Steps to reproduce

1. Pick Darius and have some random champion on the opposing team,in my case it was a Riven.
2. Make sure to load into summoners rift with deathfire touch as your keystone mastery
3. Autoattack to apply your bleed passive.
4. Notice the bleed passive is not applying deathfire touch
5. Use Q to apply the bleed passive
6. Notice that deathfire touch procs only because Q was used and that it is not stacking further due to bleed.
7. Stack up your bleed on the opposing enemy champion and pay attention to the ad ratio of deathfire touch via the scoreboard
8. Notice that deathfire touch does not take into account the extra AD you gain from your passive.

I would include screenshots but I didn't bother to get it when I noticed this wasn't working as intended. I will get it when I get the chance.