For those of us with the smaller install(my install folder is 13.1 GB) we can get it to 3 DVDs.
1. Download and extract the attachment in the
first post by REV0(there should be 20 GB of free space where you extract it to be safe).
2. If you don't have the US version follow the instructions in
Ciapa's post.
3. Rename Data2.lst to Data2b.lst
Rename Data3.lst to Data2.lst
Rename Data2b.lst to Data3.lst
4. Delete autorun.inf and setup.ico from HOTS_4
5. Follow instructions by REV0 in first post(don't create ISOs - you'll have to do this manually).
6. Move everything in HOTS_4 to HOTS_3
DVD1=4.28 GB
DVD2=4.29 GB
DVD3=3.64 GB(what language you have and the amount of save data will change this but it shouldn't be a significant difference)
Tested and working.
Edit:
Also, for REV0, my StarCraft II directory dump is attached. This is not needed for the conversion.