Comes down to what your tank is doing for the most part. You could probably make an argument for any DPS to carry some Pen gear for when they get into a group that is just clueless in terms of group pen buffs. Usually, Pen is your best source of damage until you get to that cap, so if you really are getting no help from your group, lover is probably your best option.

That said, most groups outside of a random GF will cover the basics of Pierce Armor and Infused crusher. A high percent are going to run something like Crimson Oath or another pen set. If you really want to cover yourself, you are probably better off carrying some sharp weapons in case you need them once in a while rather than constantly messing with your mundus stone.