1) Users on Xomba may still click your links there and come read your hub
2) Xomba links are indexed rather fast into Google.
3) While the Xomba links are nofollow the Xomba page containing your article summary may rank highly on Google for your targeted keywords. Since this page has a link directly to your hub it will still direct traffic to your hub regardless of nofollow.
4) I really do not believe that Google totally ignores nofollow. Just my opinion. Some have supposedly ranked very highly only from using nofollow backlinks.