Kaivax, a WoW forum community manager, revealed that WoW Classic's class design, battleground mechanics and stats on existing items will be set to their 1.12 state, despite the game releasing content that expands beyond that. This removes "progressive itemization," so if the stats on a specific piece of equipment was changed during the original updates, that won't take effect in this version.
The Horde levels 50-60 guide has been rewritten and revamped. My 1-60 Horde leveling guide is now completely updated for the 1.12 Drums of War patch. As you can see it is about 15% larger than the 40-50 guide (single largest guide page yet). There is also a lot of route changes. I moved the entire Silithus section from level 55 to level 58, which allowed me to include a lot more quests for that zone. There is also a lot of other improvement to the route, including adding a lot more quests into the guide, mostly from Moonglade, Silithus and Eastern Plaguelands. This will make the final level 59 grind much shorter.
So committed, in fact, that modern WoW players are trying the beta and reporting what seem like bugs today but what were actually intended functionality 13 years ago. This became such a common occurrence that Blizzard publicly posted a list of known non-issues called the "WoW Classic 'Not a Bug' List." For example, hitboxes for the Tauren player race are much larger than those of other races. In a modern game, this would be seen as a serious balance issue (see: Apex Legends). But it's what vanilla WoW was like, so it has been faithfully reproduced.
All of this is keeping with the spirit of vanilla, which I think is more important than that a specific number be 11 instead of 12. And it would help to "resize the swing" by making the game harder to the more experienced community, and forcing people to re-discover the game rather than simply looking up whatever they want to know on a spreadsheet somewhere.
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.