HotW gives some crit, dodge, and health.
NV gives a 10% healing boost while active.
It makes sense for DoC to have a "tanking" boost in addition to the raid-healing part. Especially when you consider that 10% crit for mangle amounts to 60 rage once every about 3 minutes, so it's not terribly big. It's also still a small DPS increase relative to the other two, a ~6% damage boost to a skill that's ~30-40% of our damage on a good day.