You're right that not all of the job would require personal contact, but I think much of it would be easier in person.
I suppose Larian could add a patch creation step to the build process, but there could still be a great deal of data produced between builds, requiring large downloads or mailed CDs/DVDs (that would take a week, at best, from Belgium to North America).
The problems getting many builds of a presumably multi gigabyte game halfway around the world in a timely fashion (so it was always up to date) are not insurmountable, but doing so would introduce some security concerns. I don't think Larian would want to let their code outside their offices until it was fairly close to release.
Collaborating on WC3 RPGs is simplified by the fact that everyone involved has access to the World Editor. Larian is using various proprietary or custom tools. Neglecting security concerns they could provide their own tools to an outside worker, but there may be licensing restrictions on the proprietary tools that could make it impossible, or just more expensive, to install on an outside system. Of course I think a game designer would be working more with high level tools, which would more likely be Larian's programs.
Also, in collaborating online, everyone has the same delays and is working with the same constraints. In this case, everyone at Larian would be working at one speed, whereas an outside worker would be a little bit behind and take longer to provide feedback, etc.
"it just could've used a person serious about continuity/story editing."
Agreed.
