People tend to overthink secondary stats a lot when choosing gear. It's important to remember that item level is always king due to how strong main stat is. 9 times out of 10 you should be choosing your highest item level gear, regardless of what secondary stats it has. My rough rule for Leech/Avoidance/Sockets is that they're generally worth ~6 item levels. Below you'll find a breakdown of our stat priority for Mythic+ and raid. *PLEASE NOTE: Crit is prioritized higher than every stat except Haste when playing the Lightforged Avenger build.
Let's start with the basics
For the first season of The War Within, Nerub'ar Palace is bringing us a tier set that amps up our Holy Shock, Word of Glory, and Light of Dawn healing:
2 Set: Holy Shock's healing is increased by 10% and its cooldown is reduced by 10%.
4 Set: Holy Shock increases the initial healing of your next Word of Glory or Light of Dawn by 8%, stacking up to 4 times.
This tier set will have very little impact on our playstyle, as most first season tier sets often do, allowing us to enjoyed a boost in throughput while focusing on learning all the new hero talents and changes to our core kit. Remember that your first spender after Divine Toll will always hit very hard since it brings you to full stacks. It's more important than ever to dump your Holy Power both before and after pressing Divine Toll so you don't waste your tier set.
With The War Within you'll see the return of many familiar enchants, oils and armor kits as well as interesting new ones! Before every dungeon or raid boss you'll need to make sure you have everything reapplied to your armor so I suggest getting a weakaura like this as a reminder.