Kill rate is significantly faster with more people, yet exp per mob is significantly less, and so without an extremely populous camp, you will obtain far less exp, in time spent travelling/waiting for repops. With an endless flow of appropriately levelled monsters, a group will beat a single player using trust. But there simply is no location that exists like that at the moment.
If Camate really meant that some monsters give bonus exp for people in groups (enough to nullify the negatives of grouping), that could be a solution, but that's why I asked, I saw nothing to suggest that would be the case.