I don't think a skill tree or something similar would work in this game. Players would in fact find the most efficient build in no time. Don't get me wrong, I would love this to be possible and I know that this can be done in other games and that there is games that have done it and done it well (Ragnarok Online for example).

Sadly FFXIV is not one these games. Why? Because basically 99.9% of all skills in this game can be throw in a calculator and then is just a matter of time to find the "best" build. Since the only concern in this game is "How much DPS I can do in X amount of time?"

I want to be wrong, and I want them to try, but sadly its pretty clear that this won't work in FFXIV.