EDIT: I was able to get it to work after lurking in some other threads, you'll have to delete the WoW application and WoW launcher and replace them with the file from down below.
https://mega.nz/#!w953AThS!IujGFBQPL...Sgpr4RAsYgiNtk
So I'm running 10.14.3 Mojave and just downloaded the 3.3.5a Mac OSX client through BitTorrent. I saw the guide about updating but it only was mentioning OSX Yosemite and below so I was hesitant to go any further once the application file would not open.
Basically the install completed and BitTorrent gave me an error message under the "Status" section that says "Error: ReadFromDisk: No such file or directory". In addition to this, the WoW application that was installed onto my computer (the folder containing the application files) is unable to open. It has a circle with a line through it and says "The application 'World of Warcraft' cannot be opened."
Sorry if this is an easy problem to fix or theres already a support topic on it but I didn't see anything for Mojave and I'd really appreciate any help or guidance.