Note: My goal here was to create a comprehensive list of everything you'd need in order to learn to play any class (from Level 1 to Naxxramas)—meaning I am only including class-specific resources here (so no profession guides, general leveling guides, etc). Teeb's Resource list is much broader in scope, and I highly recommend you take advantage of it (as it contains a plethora of non-class specific resources as well). If you're not aware, Teeb is also responsible for the Race & Class Comparison Tool, Dungeon Tier Sets Gallery, and a huge variety of other insanely useful resources.
Some class systems from the original game simply don’t have a modern equivalent. The class probably most affected by this is the hunter. The pet happiness and loyalty systems were removed a long time ago, as well as pet training and the ability to use both a ranged weapon and a melee weapon. In these cases, converting the old data to the new system wouldn’t work, simply because there is no new system to match. In this instance, we had to bring back the old code—and we did. Fortunately, the restoration went smoothly, though the reality of having to buy arrows or feed their pets again took a few people in our internal tests by surprise.
Swim Speed Potions (used especially at lvl 37 for Faldir's Cove in Arathi Highlands and lvl 57 in WPL). Try to get multiple stacks of these. I also recommend keeping a stack of these always in your bags. You will frequently pass rivers and lakes and can use these potions to pass them faster through out the guide. Please note that these potions do not stack with Druid's Aquatic Form and Glyph of Aquatic Form.
I made some route changes to the Horde levels 43-44 sections. I have swapped 44 Dustwallow Marsh with 44 Desolace (the entire sections). This allowed me to do Deadmire (at lvl 43 instead of 38) and then go stop at TB to turn in Deadmire + The Black Shield at the same time, then fly quickly to do the Desolace stuff. Doing 44 Desolace is now mandatory because I think its faster with the new routes. This will also make the level 53 grind much shorter. I think these were great changes.
Other decisions were slightly less clear cut. At one point in WoW’s history, there was an 8 debuff limit on any one target. This was later raised to 16, and today there is no debuff limit. Thes change radically changed the balance of classes and strategies players could employ when using these debuffs to overcome content. To preserve that balance—and to avoid the slippery slope of retuning patch 1.12 data to compensate for such modern-era changes—we’re looking at setting a debuff limit of 16 for WoW Classic.
There’s the reason why some players used to call the game World of Roguecraft. Rogue was one of the most popular classes in classic WoW and there’s a good reason for it. During vanilla, Rogues topped DPS meters in raids and dungeons, but their main strength was world PvP. Rogues could stealth through enemies avoiding unwanted engagements with the opposing faction. Additionally, a huge variety of crowd control abilities and high burst damage made them the worst nightmare for the cloth-wearing classes. However, Rogues were in a bit of disadvantage regarding end-game gearing since most of their gear pieces were useful to other in-game classes as well.