You have been in Turn 5 yet have not beaten it. You claim this game is easy. This seems to be a contradiction.
Tanking is not stressful at all once the fight is learned. Learning a fight is stressful for everyone.
I have all three roles leveled. Healing is by far more stressful than the other two combined. DPS is only stressful if you seek to maximize DPS. Tanking is nothing in comparison.
It isn't surprising that you have no difficulty in turn 1-4 as BLM given the above. Think I'm biased? Think again: my main is BLM.
You seem to have trouble with Titan Ex, though. I do not find him to be difficult. Are you a person who also uses enrage for turn 2?
You have no tank leveled. You cannot speak for tanks in endgame content. You are assumed to use SMN as well meaning you have no healer leveled. You cannot speak for healers in endgame content.