The proc* from your trinket appears to be:
http://www.wowhead.com/spell=138786
I suggest making a stand-alone icon just to show the pressence of buff 138786, to make sure it turns on when your trinket procs, sticks around for 10 seconds, then falls off once it's done. You can add the constraints and fiddle once you have that basic icon to work against. From your post, I think you've done this already (grats!).
So, you're monitoring spell id 138786. You can do this as a stand-alone TMW icon (buff/debuff -> buff type | player), or as a condition on an existing icon (again, buff/de