Lvl16 is fine for the mines 0.o, there is a step up in difficulty in dungeons compared to fields which makes partying more attractive, but having said that, I still solo mines1 easilly at 15>
Or were you saying that they should be lvl16 but arent? Because I did most of the quests and bosses in the low areas, didnt grind really besides for quests and by the time that was all done, I was 15-16 and ready for mines. If you get there before you hit 15-16 then its time to go back and look for more quests/bosses/gear. I dont really see any issue here at all.