All the info I have on this is from my one personal experience with the Gustaburg garrison. We had 12 people. I can't remember the exact jobs but we had 4 WHMs, 2 BLMs, 4 NINs, and the rest I can't remember exactly, but we had as many blink tanks as we could get, and then some random melee in there too.
The first wave is pretty light. We had 1 WHM in charge of only healing the recruits (there were tons of them) and the rest of the WHMs just traded off healing/medding. One NIN would provoke a casting quadav and kite it around Gustaburg while we killed off the other quads, then when they were all dead except for that last one being kited around, we'd med full and the NIN would bring it back and we'd kill it. Then about 20 seconds after the last quad is killed, round 2 starts. Rinse, repeat. NIN kites one around so we can med full before the next wave. Each wave there are 4-5 quads I think, I can't say for sure though.
I can't remember how many waves there were but I want to say 3 (it's been months since I did this >_<). The last wave is harder because the main NM quad spawns too (Lead Quad), so the kiter NIN would wait until he spawned and would kite him around until we finished off the rest, and then bring him back for the last kill.
We got increasingly better at this the more we tried it, and even had a round where no recruits died. It seemed like the loot got better depending on how many recruits survived, but that could have been our imagination. We did it 5 times and got plenty of Mannequin parts (everyone got feet, but only a few people got legs), a good amount of garrison gear, and about 5 of those exp scrolls.
Melee should have some au laits and mages should have melon juices (Yag drinks are almost overkill at that level), along with your other typical foods. We used Hi-potions a few times too until we got good at it, so those aren't bad to have either. It's nice to have someone who has warp Home Point in Bastok and teleport back out to the outpost to run for any supplies you might need (has to be a Stok citizen) like Hi-pots or juices etc. This is an item heavy experience until you get good at it. I think the first time around I used 3-4 juices, but by the last time I had it down to 1-2 juices.
Sorry I don't have more info for ya, my only knowledge comes from doing it 5 times that one day months ago :P It is a fun thing to do though, and I'm sure some of the other area battles may be different, but for us, the kiting method worked like a charm.
Edit: And here is the only link I know of. This is what I looked at before trying the Gustaburg one so long ago...
http://mysterytour.web.infoseek.co.jp/ffxi/us/tips/garrison/garrison.htm
Edited, Sat Nov 27 12:49:45 2004 by Apocpink