Ugh... Why don't people intelligently think through things before posting things like this. What do you want? A completely unpredictable boss battle on the difficulty setting of coil? It would be unbeatable. Like, its not even a "well, if you are skilled and can react fast blahdy blah blah" no. It is simply unbeatable, no one would ever beat it if they can not strategize because they can't know what is coming. In every MMO. Every. Single. One. Bosses go on a pattern and by phases, so... welcome to MMOs I guess. I am assuming this is your first one.

If an MMO was to use completely random boss attack patterns each time, each attack would need to have a very long cast time so people could actually place themselves or whatever they have to do to react to it, which would just make the fight boring and dumb.

The OP seemed to be made without understanding how games work at all. So, its just a no.