in short this is what its like to fight an AI (npc). If boss does this you should do this. And if you do this the boss responds with that.
If the bosses where controlled by humans . then the OP would get what he/she wanted :P ( but this isnt the reality in ff14 )

So either you do it as they build it , or you dont do it. simple. And if all the encounters could be done on first try, ppl would become bored and leave the game. So there is a fine line here to adjust. Not an easy task , but so far I think SE is doing a great jobb regarding endgame boss encouters. compared to other PVE focused MMO's