If the only thing you were doing was casting Barspells, that's not surprising at all to get only 60 exp.
White magic buffs are 20 points per action, with a cap of 150 points. Players between levels 16-30 only receive 40% of their points as exp/AN when tags are turned in. So, assuming you capped on your buffs (which is done within 8 spells and thus the MP of the other RDM doesn't really matter), you'd be getting: 150 * 40% = 60 exp
With Barspells alone, I believe you'd be able to turn in your tags every two minutes instead of six if you were of the highest Campaign rank to get this amount since the point cap would exceed the maximum for that buff (82 points/minute * 2 minutes = 164 points > 150 points).
ThistleChaser is getting a higher maximum due to both a higher level (he says he started at 38, which would be getting 60%; LV46+ would be getting 80%) and doing multiple types of actions. As a WHM/BRD, he is likely running through:
White magic buffs to self - 20 points each, 150-point maximum
Bard songs to self - 20 points each person receiving the buff, 300-point maximum
White magic buffs to NPCs or PCs - 10 points each, 300-point maximum
Holyknight with 6-minute tags at 40% gain (LV16-30) would get 492 * 40% = 196 exp maximum. <= ~400 points is not possible if this is your level range
Holyknight with 6-minute tags at 60% gain (LV31-45) would get 492 * 60% = 295 exp maximum.
Holyknight with 6-minute tags at 80% gain (LV46-60) would get 492 * 80% = 393 exp maximum.
Holyknight with 6-minute tags at 100% gain (LV61+) would get 492 exp maximum.
Then it's just a matter of figuring out what's the fastest way to hit the cap (492 points) for that time limit, which is probably just 8 Barspells, 15 Bard songs, and 5 Protects/Shells on random NPCs or PCs.
Sources:
http://wiki.bluegartr.com/Campaign_Point_Calculation
http://ff11wiki.rdy.jp/-2122710428.html
Edit: It begs the question then of what exactly the OP should do in order to get the most out of Campaign, and sadly due to the fact that most buffs and debuffs require TP--which you won't be getting at that level range--there's not really much you can do. On paper, it looks like a DNC27 would want to sub BRD and cycle Minne > Minuet > Paeon 4 times (12 songs total) and turn in tags every 3 minutes to get 96-98 exp. At 31+, you'd probably want to do 5 cycles instead (15 songs total) and turn in tags every 4 minutes to get 180 exp.
Though, this comes with the caveats that:
- I've not tested it myself using DNC (leveling on pets was easier for me)
- you may get 0 or 40 points towards your self-buff cap by using Spectral Jig (whether it's not counted because it's considered an ability use, or considered as receiving the separate "buffs" of Sneak and Invisible...if those are even considered "buffs"). Naturally having another point source will decrease what you need to do to reach the cap at either level range.