Comment by annnoo

Yes kind of. You have to differentiate between all the different kinds of data. A lot of data was already included in the client files, but for the rest you had to sniff packages, analyse combat logs, watch 360p videos of boss fights and try to figure out exactly how mechanics are working. It got very ugly after a new expansion has been released, because it was not possible anymore to sniff for the older expansion.

It was always a “best effort”, but also very rewarding if you got a specific fight “somewhat” close how it was on the official servers.