dia-0.94 contains a bug that results in bad font sizes when exporting diagrams to png or eps - for details see: http://bugzilla.gnome.org/show_bug.cgi?id=153609
Created attachment 50726 [details, diff] font size workaround patch
Created attachment 50727 [details, diff] patch for dia-0.94 the ebuild applies the font_size patch
dia-0.94-r1 is in the tree now and it includes the patch on comment #1. Thank you for the report and help.