I’m not talking addons, that happens every patch and the creators will (hopefully) get around to fixing them in time. I’m also not talking default Blizzard customizable UI, as that is its own special can of worms (and generally solvable with addons). Mostly, I’m talking actual gameplay elements. Though, I will say, the option to “use raid style party frames” disappearing boggles my mind [edit: I found the option, just wasn’t where I was expecting it]
Some things I’ve noticed:
Discipline Priest. Bottom of the talent tree is a talent called, “Void Summoner.” It reduces the cooldown of your Shadowfiend by 6 seconds, or Mind Bender by two seconds. Two separate uses, depending on which one you have. Except, Mindbender is a pre-requisite, which replaces Shadowfiend, so you literally cannot have a Shadowfiend. Moreover, Mindbender doesn’t work, so you do actually have Shadowfiend anyway. But the talent doesn’t work, and you don’t get any cooldown reduction no matter which talent you choose.
Prot Paladin: Avenging Wrath does not let me use Hammer of Wrath. Hammer of Wrath still works against low health enemies. Not sure if this is prot specific, level specific (tested at 45), or a combination of talents causing the issue.
Dropdown menus (like mage teleports and portals) only work from the spellbook, not action bars.