I put it on last night for Festergut 25 man and I forgot to switch it out the rest of the night and I saw something that did not gel with what I've seen previously in that the trinket got to a 10 stack and stayed there for every fight I used it on.
If it stacks more often now, I have to say that it's been substantially buffed and is now most likely the best tanking trinket in ICC.
Fixed the title for clarification- Ron