i'm not going to fight over the severity since but http://www.debian.org/Bugs/Developer#severities says
important a bug which has a major effect on the usability of a package, without rendering it completely unusable to everyone. i'd say this bug fits that definition, the main binary is incapable of performing its main function and the jigdo-file/jigdo-lite workaround while ok for those with very fast stable connections (or a local mirror) who have no need to keep tabs on progress etc is basically unusable for the rest of us. unfortunately c++ is not a language i'm familiar with or i'd offer to help. maybe you should tag this bug help so that those looking for packages that need working on find it.
