Deathfire Touch Logic

I've... been wondering if anyone really knows the logic behind DFT yet since it seems Riot has, like, a check list of what works and what doesn't work on it and it just... doesn't make sense to me anymore.

On the PBE, it used to proc on everything that wasn't on-hit damage, like Ez's Q and GP's Q would still proc it like any spell, but Teemo's E, Varus/Kog's W's, etc. wouldn't proc it because they were considered 'on-hit' damage. That seemed perfectly fine, but sometime between the last week-ish and the release of pre-season, it was changed to be only on things that normal proc'd spell abilities. I figured, okay, they wanted to make Ezreal very sad, no big deal though.

Now I've played a number of games and noticed Teemo's shrooms do not apply DFT... His -shrooms- do not. I figured, okay, maybe some bug with spawned things? Well, Zyra's plants proc them so I figure it's some weird off the wall bug... then I play against a Heimer with DFT. I figure, weird, his turrets don't proc Rylai's or anything, so that wouldn't really work. Come to find out his turrets, while still not applying Rylai's, were applying DFT... Okay. Where the heck is the logic here now because it's one thing for it to not proc on On-Hit things like Teemo's E. It's okay that Ez and GP can't have nice things... BUT WHERE DID THE LOGIC GO WHEN HEIMER TURRETS GET TO PROC IT AND A TEEMO SHROOM CAN'T? I'm SO baffled.

Do you guys have a check list of what this damn thing works on because I'm afraid of finding something I just do NOT want to find out about like Devourer's second attack proc'ing it or something stupid.