I play a prot pally and I run alot of heroics and kara,
(the trink actually was enough to let me tank some harder stuff) this trinket has saved my ass, and the partys multiple times.  its a tank item first, then whoever else wants it next.  It dosn't matter what the hell kinda tank you are, if you bit off more than you can chew, you will need this to give the healer a few seconds to get your health back up, and give the party a few seconds to down a few mobs and get you back to a number you can handle.  you can ramble on endlessly why certain "classes" need it more...whatever...  if any class is taking a hard thrashing, this is one thing that may give you enough of an edge to prevent a wipe.  its nice for pvp as well, very handy when you got two rogues stabbing away at you.  thank god I have a great guild and we don't squabble over drops like a bunch of old ladys.