It goes both ways really. Gaining experience points to level up jobs in Abyssea and gaining most of your in game experience from Abyssea are both pretty much the same. 97% of all NMs in Abyssea are trash that often drop useful items, and hold no real credibility toward anyone's accomplishments. I'm not saying camping kings for 4 hours a day was a challenge, but there were always NMs far more challenging that didn't always require spamming for claim. AV, PW, Wyrms, Sandworm (I guess), and many others, that, as briefly pointed out in an earlier post, were designed for large group coordination. I'd show screen shots but unfortunately I only have a couple of SS of AV's drops. I'd be glad to fight Pantokrator again without the use of a brew though, it's not difficult to figure out it's patterns (or to not screw up for that matter).
And now back on topic again...
Keeping larger scale Ballista matches in mind, if you were in or currently do reside in a large linkshell where everyone can function properly together to take on NMs and other fights and tasks, you can essentially do the same in Ballista. A major key factor in Ballista is coordination, and that's one of the reasons why some matches weren't so great. This is where you take your actual in game experience and put it to use in a new environment. Not as one set strategy, but using the knowledge of everything you've gone through. And to top it off, your equipment is restricted to one set at a time, not that you can't change it to suit your needs, but once you start fighting you better hope you switched off your main macros. I've got books of macros specifically for Ballista, mainly for DRK, PLD, SAM, DRG, WAR, THF, RNG, BLM, and RDM. I've been meaning to add more jobs but since no one wants to play mario'spunch-off with me in Diorama or anywhere else I haven't felt the need to. I want to see what my Ukon and Kannagi can do in PvP.
Random side note: ever get charmed in Besieged with Lv.3 Aftermath on around a group of unsuspecting people? BLMs and DNCs didn't like Kannagi very much.