How complex is Ninja at max level? It's not. Ninja is a pretty rote job: you do nothing for 45s, and then burst for 15s, and your burst is going to look the same 90% of the time.



It is, however, button-heavy and it is, however, busy. During those burst windows you'll be pressing a lot of different buttons rapidfire, so for your purposes -- a job that isn't hugely button-heavy -- Ninja is a poor fit. It's my personal favourite job, but I play on mouse and keyboard, not controller.



Summoner, I believe, is pretty low on the actual number of buttons, as is Warrior, but even then you'd be hard-pressed to limit yourself to 16 slots without impacting your ability to contribute to the team. At low levels, only using 16~ abilities is fine, because odds are you won't even be able to fill 16 slots until Level 70 or so, but as you level up various jobs, I'd really encourage you to make use of the extended hotbar and get comfortable with it. Doing that will dramatically increase the number of jobs you can play comfortably!

Either that, or swap to mouse & keyboard, and enjoy not having a button limit.