Current setup, To not about how I play, I pretty much hold the R2 trigger all the time, so it is a case of swapping fingers to get to L2 or just pressing L2 whilst still holding R2 to access the second bars. AoE attacks are set 'off in the corner' as they are mainly used for dungeons. I do have a separate set of hotbars set to the side just to track cooldowns, for Gunbreaker, it is mainly for Gnashing Fang.
As a reference, here is my
Paladin setup. Again, similar concept. Shield Bash and Cover aren't on the bars partly because there isn't space (though I could make room) and partly because I never used them enough to warrant them.
Hiding buttons on the R2>L2 crossbar is a common thing I have been doing for a long time and it is mainly used for things that you can track by other means, Bard's Pitch Perfect, Viper's Uncoiled Fury, Red Mage's melee combo, Monk's Coeurl stance attacks etc. I do not swap crossbars, it is all purely done through the expanded crossbar system with the only things on the double tap being Sprint and Limit Break.