Fully installed its about 30GB, Sometimes depending on what youve done ie closed down the client or paused it or hit repair, the progress bar can be quite inaccurate, plus ours seemed to jump chnks of % seemingly as it unpacked files.
But bottom line theres alot of files and we are on 2Mb internet, DL speed at about 175kb/s Installing and patching sucks for us, but better internets not avaliable so really nothing can be done.
What i will say is onve your games installed and working BACKUP the folder, you do not want to be re downloading it all again if it glitches on patch days.