Yup, the download size came as a bit of a shocker. I could download this morning (four hours ago) at my constant maximum DL speed of 1.1 MB per second, that's 40 minutes for 2.6 GB.
I actually wonder how the game could be so big (for a TTG game, that is). The problem with former individual, standalone episodes was always that every time a new episode was released for a certain franchise, you would essentially re-download a lot of the Season's recurring code, textures, environments, sound effects, music or what have you, and eventually end up with the same data stored in five places on your PC for a complete season. I had hoped that this would be different with a single game release, but I assume that the individual episodes are still intact and "unmerged".
I hope you can get the download problem under control. In any case, download speeds should be better today as the initial release crisis is over.