Using the Defaultui option for my main actionbar, there is a bug i noticed only during the Amber-Shaper Un'sok encounter. During the encounter you get transformed into some abomination and gain special abilitys you need to use. The actionbar switches to another state, but you only get an empty bar without any spells on it. The result of the missing buttons is that you cant play that encounter with rdx actionbars, since without the buttons you will a) wipe your raid or b) just die.
If you need any specific details i can check whatever information you need later this week.
Any other place / quest / encounter / whatever i checked that uses bar-swapping it works without any problem.