One of my favorite features is the Smart Injection System, which automatically determines the optimal place for your character to get started with the guides, based on your level and quest history. In other words, it doesn’t matter what level you are currently, you can jump right in and continue seamlessly with the guides. It also means that you don’t have to be a slave to the guides, they work perfectly even if you’re also leveling in instances, battlegrounds, using heirlooms or rested EXP. If your level ever gets ahead of the guide, just use the built-in feature to skip to the right place again. Very cool.
Only really to expand on Gráinne's comment as regards the 'collecting' and 'roster development' sections - which are, as said 'distinct' although they are intrinsically linked - I would like to point you in the direction of the in-game Achievements > Battle Pets > Collect tab. There are a series of achievements called Raiding With Leashes, pretty much all of which can be completed via the auction house - if you have the gold/inclination - or by completing old raids.
This Shadow Talent Build is the fastest for Leveling Up a Priest Class from 1-60 in WoW Classic patch 1.12. Spamming Shadow Damage DOTs while kite mobs will be the name of the game with this build, having the ability to sustain your health is just a bonus. You will just need to make sure you are stacking enough spirit so you don’t run out of mana often as that will slow down the levelling process drastically.
Bioelectric Blast (Deadly) - Blasts the target area with electricity. Inflicts 65,654 Nature damage to enemies within 8 yards of the impact and creates a patch of Electrified Ground. Electrified Ground inflicts 14,882 Nature damage every 2 sec to players within it. Shock Burst (Important) - Inflicts 4,377 Nature damage every 2 sec for 12 sec. Upon expiration, strikes all players, inflicting up to 26,261 Nature damage. This damage is reduced the further away players are from the blast. Electric Discharge (Healer Alert) - Wekemara discharges electricity from itself. Inflicts 13,131 Nature damage that chains to additional targets every 1.5 sec. Submerge - Upon reaching 50% health, Wekamara will submerge and summon Spawns of Wekamara. Electrified Splash - While submerged, Wekemara rains electrified water from its pool. Inflicts 21,885 Nature damage to enemies within 3 yards of the impact area. Spawn of Wekemara (Damage Dealer / Tank Alert) Charged Bite - Inflicts Nature damage to an enemy Conductive Spittle - Inflicts Nature damage to an enemy and increases Nature damage taken by 50% for 16 sec. Loot Tables