Looked up RDM and SAM which are the two main jobs I play and both have new buttons. Argh.
Are you sure they have new buttons?
For Red Mage, Jolt 3 replaces Jolt 2, Vice of Thorns appears on the same button as Embolden when you use it, Jolt 3 changes to Impact when it's available, Cineration replaces Manafication when used and enchanted Moulinet combo is one button. No new buttons.
I'm less familiar with Samurai but I believe they merged Shoha and Shoha 2 (so you save one button there) and also Tsubame-Gaeshi is now linked to the same button as Meikyo (saving another button) - you got 1 new ability on its own new button - Zanshin, so overall you have one less button than before.
I could be wrong, but I'm pretty sure like I said, no new classes have straight up extra new buttons (without reducing button bloat on other abilities) except Scholar.