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Well, if you're using the correct instruments for the songs, then there's really not much. You're going to have 2 minute ballads and 2:24 melee buffs.
Part of it may just be the pace of the events. It can be hard to keep up with a group in Nyzul, because kills are often very fast, and then people move. Dynamis can be similar.

The JAs are good, but they start at a 20 minute recast. Even at max, you're still looking at a 10 minute reuse, and that's after 22 merits apiece to upgrade them. You'll never get them to the point where you can use them every cycle.

IMO, unlocking the JAs is a good idea. This isn't so much to use them whenever they're up (though you certainly could), but more to use in conjunction with Soul Voice. Basically, use SV, and then when you reapply songs, use Troub/Nightingale to double their duration. Nightingale counters the longer singing time on Troubadour, which is usually the only reason it's used.

The other major use for the JAs is really just for Troubador. If going BRD/BLM, to Elemental Seal elegy on mobs that it otherwise won't really stick on, then extending the duration is desirable. Maxing it out means it matches the 10 minute timer on ES. However, for that use, there's no need to couple it with Nightingale. Given what you've mentioned about what you do in-game, I doubt you'd need to consider that though. Just figured I'd mention it.