In this form, there is much less wasted space and spells are no longer limited to three effects. But before we can load any database data, we need to transform the old data layout into the new one. This is not limited to spells, as almost every game system (including items, creatures, player characters, spawning, AI, and more) has had its database layout altered over the years.
You're absolutely right! I've changed the opening—I hope it gives you and your list the credit you deserve. As for those other tools, I didn't include them originally because I didn't consider them to be class specific. I'll include the Base Stats Calculator here, plus add a message at the top directing people to your list if they want a more comprehensive index!
The vanilla WoW Horde leveling guide you see on this site was originally made back in 2006 by Joana (AKA Mancow, or FuriousPaul). The guides have been tweaked many times over the years to make things "faster". The leveling guides were made because of all the messages I got from people asking me how I was able to level up so quickly on new realms. I was first to level 60 on 7 different realms (3 with Mancow and 4 with Joana), even winning Blizzard's "First to Level 50" contest they held back in 2006.
To get past these hurdles, the team looked at what we liked (art and data) of what we had and what we didn’t like (the code). We wanted to see if we could utilize classic art assets and data within our modern code and get things to play nicely together. Things didn’t quite work right out of the gate, but with some trial and error, we were able to pull together a proof of concept of how to get things to work together and have something playable. This built our confidence that we could deliver a Blizzard-quality experience with the modern platform.