Alrighty then, I did not mean for uptime estimates to be taken so litterally, I will amend it that while in heroics and raid trash pulls it proc's what SEEMINGLY is a very consistent uptime. On boss fights yes of course, it is a noticeable difference.
Anyways, all that said, that is a marvelous trinket, and well worth equipping.
Before the instance I was using Essence of the Gossamer along with the Valor Medal of the First War. The +111 stam on Gossamer was the reason for keeping this trinket which I had planned to replace with the Heart of Iron from Ignis25. However with the introduction of Black Heart I replaced Essence of Gossamer with this trinket.
In my opinion out of the list of trinkets you've given I would Choose Black Heart and Valor Medal of the First War. 126 stam is nothing to look down on and Valor Medal is just an extra damage mitigating CD to blow in a tight spot.
For a druid, the greatness card mentioned is also very nice. The agil bonus is absolutely wonderful. I normally use the black heart/DMC:greatness combo.