I use the first hotbar which has everything for my full burst rotation on. I then have a second which has aoe stuff/other buffs like invigorate, EJ and potion (and my t8 tp macro for our bard haha) on which is accessed via holding both l2/r2. Some things like heavy thrust are doubled up so there really shouldn't be issues with space. I also have a horizontal bar above my cross hotbar which has some things from the second bar on so I can see for example when invigorate is ready to use again.

You don't need three hotbars for playing dragoon unless you really like to separate things up.