This ring has a use, but is it USEFUL? Depends on the situation.
In PvE, this ring is good for late game-low SL runs where pretty much everything one shots you. Good incentive really, don't get hit and you'll have bonus damage on top of being alive.
Not good for hyper builds though, doesn't even work for hyper builds.
In PvP, this ring doesn't really work unless:
A. You have a long ranged weapon.
B. You have a fast weapon and are good at dodging.
C. You are a caster and are good at dodging.
D. You are really, really good at parrying.
E. You have a really good sense of spacing.
F. You have really bad connection.
G. You are using hacks to get infinite health.