Many of the people who are using tons of hotbars are only using half of each. They have lots of bars active just because of the layout. I have 2 hotbars devoted to switching classes and another for chocobo commands and emotes.
That said, paladin has 35 potential combat actions including limit break and sprint but not including directional movement or potions/food. There are about 9 defensive cooldowns, 2 "stances" depending on role, Cover (which is rarely used), 2 healing skills, and 6 cross-class skills. The basic rotations are 6 actions with 2 off-GCD moves, 1 ranged opener, 1 proc, 2 conditional use abilities, and Flash. So like 13 base abilities to keep track of for attacking and 11+ for defending. The rest depend on how often you use them and what cross-class skills you take. Realistically expect to be keeping track of 25+ actions in combat by level 60.