Are you on some bad DSL or something? The game is supposed to be about 50 GB in size. Over 100 hours (1%/hour), you'd be going at a DL rate of 1.14 Mbps, or an entry-level AT&T connection (probably the 1.5 Mbps service). To contrast, I'm on Comcast. We have a 75 Mbps connection that usually runs at about 90 Mbps. You're never really going to get the Xbox to leverage the entire connection on a DL, but let's say I can get half of it going, 45 Mbps. That'd make the game take a hit over 2.5 hours to install.
Now, there was something on the main WC site about how the game was taking well past 100% to install, but since you made it sound like it didn't progress to 100%, that's probably not the same story here. I'd just guess you have a mediocre DSL connection, which you can check at
Speedtest.net by Ookla - The Global Broadband Speed Test.