I don’t know any person with the right mind that would wear Staff as Resto or Ele in PvP or even in PvE when there is 1h and shield available. Maybe for RP reasons.
Shield gives 1/2 of the armor all other items give so it’s around 10% phisical damage reduction. While in raid or M+ it might be viable early you won’t wear it ever if you push higher keys because you lack other damage reduction than Astral Shift and 20% from Primal Earth Elemental if you spec into the talent (and currently people don’t). Blizzard please stop giving us Staffs as rewards at least in PvP. It’s just stupid.
Yesterday I was offered a choice between 217 trinket 217 boots and 223 weapon from the great vault. And instead of being excited I got a huge weapon upgrade, it felt bad because it was a staff. I talked myself into picking it, because a 223 weapon is a big power spike, but it still felt so bad. Its like giving a fury warrior a dagger. At least we can transmog to legion artifacts so I dont have to look at a mail-armor clad Orc wielding a walking cane.