Actually the main issue with raiding in FFXIV is that classes simply don't have enough specialization tools and utility abilities.
In the old days of MMORPG (and RPG), you had countless classes, abilities and ways to tune your character (dark souls and demon souls works that way too). On the other side, you had bosses which were doing their abilities (here again, think dark souls) but didn't have particularly exotic patterns (they were mostly stronger normal mobs).
As a player you then had to come up with a way to specialize your character and make a clever use of your abilities (whom you choose by adapting your team comp, as an example), by finding a strategy (based on the skills you were using) in order to kill bosses. There were usually more than one or two (very different) ways to kill any particular bosses.
The main issue of FFXIV is that you cannot really specialize your character, there aren't a whole lot of classes and the classes aren't very different from each other, in any given role. Plus the number of (utility) abilities for each classes is very low. Furthermore, the very low number of players in a party doesn't allow for a whole lot of variation in a team composition, thus limiting the number of possible strategies (but, here again, as there isn't much differences between the classes of any given role, this doesn't make much differences in FFXIV).
Therefore SE had to come up with raids whom the completion didn't trully depend on a strategy invented by the players, by coming up with a clever team composition or abilities combo, but rather on artificial ways to decide the success or the failure of an encounter. These artificial ways includes bosses in which you have to move a certain way in order not to wipe (almost every bosses from T5, as an example, the P4 of the T9 is a staple of those bosses in which you re more dancing than fighting).