It's probably because there's going to be more ways to get Soldiery, and that these dungeons (like Brayflox HM) are done very quickly as people get better gear (which will also be easier in 2.3).

It also encourages higher geared players to use the newer dungeons rather than the old ones.

This is also something that is done every patch. Easier content gives reduced rewards, and as the average iLvl of the players increases, the speed of acquiring those rewards also increases. This is the alternative (and better for the game in the long run) than simply increasing the caps higher again.