Very much depends on your class and build, for some classes yes it is. For others no definitely not.
for aps classes like sins and BMs its helpful..but for arcanes...its not worth itif I went lunar cape for -6% channel on my wizard, I would have less than 30k hp (28k hp I think).considering that we can be instantly killed easily, there is no point in sacrificing the crucial stats from a dragon cape for an extra -6% channel.besides. If sharded correctly, you can get a -69% channel on a wizard (demons can hit -89% with demon wellspring quaff). which is good enough