You don't have to wait for the DLC if you bought the Deluxe version, it is included as if it was all one game. When you download and install The Deluxe version you will find Rogue Realms faction and maps already there.

You are correct that the original Hero's Hour is a 671mb download and the Hero's Hour Deluxe is a 336mb download even though it incudes Rogue Realms. That does seem odd. If you look at each of the game pages they both need 100mb space though. It looks as though some "near enough is good enough" was used for the accuracy here.

Anyway, if you have the Deluxe Version - Rogue Realms is included as part of it. At least it is with Offline Installers, I don't use Galaxy.