Except that parties aren't really getting anything from partying. They're not getting a bonus, they're not getting exp chains, they're just killing higher ranked monsters. It's not a bonus for parties or even a penalty to soloers, like everything in this game it's all about level difference. No skill, no stats, only rank vs rank. Party isn't 'influenced' at all except that you have more people to throw at the high ranking monsters and a few more hp/mp.
