I've been looking at this trinket and argueing with my tanks over it's value for a while. The non-heroic version is 24 stam and ~1900 armor, but i think it's awesome.
What some of you are missing (and you are all better tanks than me, so dont' think i'm hating) is that the buff ONLY REQUIRES you to be hit ONCE in a 10 second timeframe to keep the buff refreshed. My tanks never go 10 seconds without getting hit at least once. Maybe you guys do.
The only question really is how long it takes to get to a 10 stack. IMO, this trinket rocks.