For DPS I get it. Stuns, slows and interupts (after 7.1.5 at least) work with the ring. And that should be the DPS's utility: to CC.
DPS do damage and have CC utility.
Healers do healing and have defensive utility
Tanks take damage and have a mixture of CC and PERSONAL defensive.
That im my opinion is a VERY BASIC and GENERAL outline of the roles.
But healers bring a different dynamic to a group. They aren't really there to provide major CC in my opinion, they are there to heal and provide defensive utility to a group, such as Tranq or Sacrifice or Blessing of Freedom-esque abilities.
Healers cannot interupt and have very limited CC, so why have a gut-wrenching terrible legendary given to healers which just makes their experience rubbish?
Im not crying about not getting a BiS legendary which gives me bigger numbers, I would love to have Uther's Guard drop (which is pure utility only, no HPS gains). I just dont understand my Blizzard added Sephuyz to healer's loot spec when it wont be used nearly as much as a DPS would use it.
TL:DR - if a healer gets Sephuz, they can't use it and therefore it is useless. No fix or buff can change that unless it is fundamentally redesigned to cater for every role and spec.
Edit: I am not a frequent user of the forums and im just voicing my opinion. Im sorry if this has come up before or something else troubles you, just voicing this concern!
EDIT 2: SORRY! I meant int he context of raiding. Good luck trying to stun, slow a boss :P