Class specific macro's would be annoying in my opinion, mostly due to the fact that I use them to change classes, It'd be a pain to make and change the class changing macro's for every class. (gear updates included, it'd be a bit of a hassle.)
I personally use a controller, so I can only use the macro bar while keeping a shoulder button pressed, so I won't accidentally use it.

Still I suppose if you use your keyboard and macros there might be cases you press ctrl instead of alt or something and use the wrong macro bar.