actually they have nearly everything is readable from castbars, boss-emotes and animations. as a melee i tend to watch boss animations a lot, because its a big tell whats gonna happen, its an old habbit back when there were no castbars in the game. did u know for example that lady vashj hands lit green before she (or the bats/bird) do the ae u have to doge as melee? Did u know that shadowtrap had a unique animation at lk? And last bat not least, a clock for timers was introduced in the standard ui. Pvpers use it quite a bit.
Addons make this more readable and easier to acess in form of timer bars, which is good. If they tell you exactly where to run, not so good.