Queue times are way longer for low lv dungeons compared to high level ones, when you are waiting for a tank. I would guess that not many lv50 players do the low lv roulette, because the 60 soldiery tomes it offers is simply not time-effective versus other content where more tomes can be gathered faster.

Consider that lv.sync is applied to low level content so that prohibits overgeared players from clearing faster, unlike other kinds of content that offer tomes. For the amount of time it typically takes to clear, shouldn't the soldiery bonus be raised to 100 or higher? Then more people would be incentivised to run this roulette, and thus new players will be able to enter dungeons without waiting for hours.