The point of the reward is to get people who've done those duties in there again, as there's no gear drops in that duty that would bring someone back.

The issue you were running into is not the developers for trying to make sure you'd have anybody running Castrum and Praetorium at this point, it's on the players who felt the need to yell at you for the very thing they did when they first entered Castrum.

Praetorium isn't much better. Honestly, I'd suggest trying to get a Party Finder going on your server asking for a group, offering your first time bonus as a reward so that you can experience Praetorium without the vitriol if you're worried this will repeat itself.

(Also, you can edit your post to get around the limit)