i think they should calculate the exp you get at the end of every 10th floor based on the amount of enemys you killed and chests opened. if you skip everything, you will get no exp. and yes, it's also not the very best solution to force a party of full 99/99 people to open all the silver chests, but i can't think of a better solution. skipping everything is nothing wich should be rewarded, especially when you skip over the objective of other people.
do the content and you will get exp. skip everything, aka not doing the content, and you will get nothing. simple as that.
yeah, and random partys exists for a reason too. and i don't think the reason is to let the playerbase fight against each other. then PotD would be a pvp zone.