Using Wine will perhaps be your best bet due to performance but it depends on your graphics card and drivers. If you are running a 64-bit install of FreeBSD, there is some complexity with 32-bit libraries. Let me know if you do attempt this and run into issues.
Or the hidden third option:
3) Ask Blizzard to make an official FreeBSD port (and preferably release the client and server software open-source XD)
I've never tried it, but Blizzard does have a tendency to create games that work well under wine.
I've tested both Diablo 3 and Starcraft 2 and they work fine using wine.
I suspect the same will be true for WoW (especially considering the wine DB entry).
Assuming you were asking me, I simply installed the blizzard launcher and installed the games from there. It's been a while though (probably a year or so).
Basically the same process as on Windows, though I remember having had minor issues with installing the launcher. There was a workaround for it on the wine app db if I remember correctly.