I'm guessing it won't make a drastic difference, I don't pvp much myself, but if I recall, warriors were by far the worst for us, and that's due to a good chunk of their armor passing abilities. Adding more armor wont help at all on that.
On the pve front however, It means I can soak on IJ on a 30 second cd now without too much concern and warbringers have become a tank and spank solo now.
It helps us live longer, and I can feel the defensive increase. Unfortunately, it does not fix the real problem with shadow in arena that any casting at all is penalized severely.