I personally have found no lack of people wishing to party. This is how I have managed it, and because I put together my own groups and pull I can be selective about the types of classes I invite (mostly mage/melee balance)
the Search function in FFXI is incredible, DO not, trust that people without Seek, do not want to party.
when I am level 30/20 whatever I look for people in this method
Lvl 29-31 -> Search Region - I scan the list for ungrouped people and check out the classes, send invites in tells to any ungrouped that fit my groups needs (tank/mage etc), if I can't find a class I want I narrow my search to their job, but widen the scope
Lvl 29-31 -> Search World - or -> Search zones right next to my region. Almost Every time. I would say 7-10 times, I ask a WHM to party who is 4-5 zones away from my group, they take the time to travel, same thing with almost any other class.
I have averaged 2 lvls per night (about 4-5 hours of playing, at all level ranges, from 10-31. I may eat my words when my rng passes into the upper 20's again, But as a theif, I had no problem creating groups that had good success.
If you also use the EXP Party comment option place information like this
@5000 (xp to level listed) Speak jpn/eng / poor whatever
Khazam Pass -Mea Holla Dem GC-(gate crystals)
Dagger - Bow - Rng Acc +15
This lets people like me, know how far you are to level, this is important, when you need to keep the groups levels Below a certain point so that Exp doesn't junk out when the VT's turn T to the lowest member of your party. It lets them know what weaponskills you can bring to the group and if a WHM can pick you up and take you places once you crest lvl 36 to join a group anywhere in the world. With choco's + Gates Travel time to any zone in the world is less than 15 minutes unless you are required to wait for an Airship. You can always shift your level search to make a party in 3 ways. as well if you are level 30, go for 30-32, 29-31 or 28-30 Also - As a pointer, if you create groups, make sure your Tanks are the highest, a 28-30 party with 28tanks and 30whm, is bound for trouble, but 30 tanks 28whm, you are golden. If anything is an absolute in FFXI its the amount of people who join my groups who say they NEVER get good groups or invites, People are out there, Search.
Last night, I went from 16-20 in 6 hours. My group went from valkurm to Korroloka - in Korroloka it ended up being Rng/Nin Brd/Whm Whm/Blm Drg/War Nin/War - we netted 5kXP per hour with only 5 players. These were all people outside of my girlfriend who plays together with me that I've never met or grouped with on fairy before, this is capable every night for anyone.
Tyrian: Fairy Server