Your composition is fine for T4, you'll have to adjust the strategy a bit from what you usually see in videos but it's perfectly doable. My usual party composition is PLD x 2, WHM, SCH, BRD x 2, MNK, BLM which is almost identical to yours and we have no issues clearing T4. Well actually we make our OT go WAR instead of PLD as we found it to be easier that way but we can do it with PLD x 2 as well so i'd say you are fine, you just need to get in and start practicing until you beat it.