So far you did everything right. Unfortunately it is very complicated (see those 11 steps in the other guide) to add those voice files to the base game. Adding them to another mod is the same way you added it to the devkit.

A much easier way then those 11 steps is to simply install and play my Bare Geomod modding set up - it is the main game with a number of small fixes and already includes these voice files. It also has all factions available to play from the start.