I hate to be the bearer of bad news on this one, but the devs did fulfill the quoted promise.
Look at the date of the patch, and what has come after that point. The “intended system” for assisting with higher level delves was the release of the deed system and the increase of kingdom levels to 15, bringing 50% faction hoard bonuses.
Just be sure, I looked this up…
… and yes, deeds did come later in the year, just as the devs promised.
Your point may still be valid in general, but that’s not the droid we are looking for.