I made an insanely simple WA to track the draw(proc) of the Hellfire trinket, you can use it for any other trinket by just changing the name from 'Hellfire' to whatever deck you are using.
This was the best I could find so far but it's really unfortunate that the buff has no timer so using %p will never track the timing of the buff. is there any way to manually add a 20 second timer to it or something similar so we know when the buff will transpose? It's really impractical having to keep track of when the last card switch was.