My focus in shadowlands will be raids and pvp (wpvp and arena).
The idea is to be a rdps in raids and wpvp ( spriest or elem) , in arenas i will respec to healer (hpriest or resto).
I wonder if spriest is a good spec for wpvp because yesterday when i was leveling my lvl 50 spriest (from bfa) i almost died to 3 trash mobs - i had to use defensives, shields and kite. I imagine if instead of a 3 mobs it was a ww. Will it get better ? This situation is a bit strange because in this paladin i pull 10 mobs at the same time and kill them in a few seconds.
On the other hand the kit of disc and holy priest is simpler than resto shaman. Resto shamans kit is to extensive in my opinion, it has about 8 totems, purge, cleanse, slow, interrupt,hex, spiritwalker grace sometimes in the heat of the fight i get confused and lose games because i didnt use a totem in the right time. Looking at the priest’s kit it almost has no utility (only 2 or 3) and i could focus more on healing itself.
TL:DR -> Choose whatever aesthetic and fantasy you like the most because both are great.
Spriest and Elem are both great picks for raids AND wpvp. Literally both are great options for both types of content.
For wpvp I believe Spriest is better at 1v1 scenarios since it has more defensives but Ele shaman can burst down someone instantly if you do your combo correctly.
For raids both do a lot of damage. Shadow priests are single target damage kings this patch but they are getting some changes/nerfs next patch so we’ll se how that affects them, they will probably still be very good. Elem Shams are at the top too.
Now for the healing part.
If we are talking only for arenas as you mentioned Disc priest seems to be top tier next patch. The new talents they’ll give Disc priest are just what the spec needed to go up to S tier.
Holy priest are S tier in this patch, but they are getting some nerfs in 9.1. I think they will be an ok healer still like B+/A tier.
Resto shaman on the other side are just ok healers for arena. Nothing special.
But if you ever wanna try raid healing or dungeon healing, resto shamans are gods here and are way more demanded than a priest healer.
R shammy is still considered S tier (or meta). If you want more invites to heal keys then play R shammy. In my opinion if you want to really do well as r shammy be prepared to learn, know and do interrupts. As for holy priest, it is bottom of the barrel. This is not to knock people who play it well–but holy is at a disadvantage in a lot of ways. One thing though, it is probably the best healer to learn on. As for disc, I main it and love it for its novelty. It is really a combined rdps and healer, with absorbs, and damage reduction. I think it is super fun in M+, but requires a fair bit of patience and practice to master. That said, in raids, it is a one trick pony–do your thing at a certain time, and then sit tight–and that can get dull.
Holy isn’t exactly a walk in the park healer either because you have the most amount of healing buttons ingame and it’s a matter of figuring out which tool is right for the job. Your legendary requires you to keep up 5 stacks that you have to refresh every 20s with flash heal.
Your primary raid utility comes in having two of the most powerful healing cds (divine hymn gives +20% healing for 15s to the raid and salvation has the highest healing output) and soon-to-be buffed symbol of hope. Your secondary utility is with mass dispel, dispel, and life grip.
Holy can get the job done in PvP, raiding, and arenas. It’s looking to be a much stronger pick next raid tier and the playstyles going to end up changing a bit in 9.1 with PvP talent changes.
I wouldn’t say priest doesn’t have utility. If anything, it has some of the most versatile utility kit of all the healers. Defensive dispel, offensive dispel, mindgames, mass dispel, mind control, aoe fear, censure/chastise, pretty good dps for a healer, guardian spirit, power infusion and probably one or two more things I’m not remembering. Holy also gets 1 aura mastery baseline, and an aoe one when talented that makes your team uninterruptable.
i don’t think any class can control someone into a freeze trap or ring or frost except maybe a class that has a pushback.