Question in regards to end game gear (Healers)

[EaMett]

Yeah I did mention piety and vit as things to take into account.

you can switch out the genji 340 ring and go with the 2x tomes (one 340, one 330) combo.

Actually that's a good catch. The 330 Allagan ring is better than the 340 genji. Slight oversight on my part.
The chest is still inferior though. I also have absolutely no use for piety at this stage which makes the chest piece unattractive to say the least. Even the HP bump is pretty insignificant.
If I need more HP and/or piety for whatever reason I would swap my pentameld 320 bracelet for a 340 one rather than fool around with my chest piece.

It's worth noting that optimization is also very subjective. You might want to optimize for dps, or for healing while disregarding dps, or for your party comp etc. These will all yield different results. But my original point was that regardless of what you decide to do, it is absolutely possible that a 320 item could be better than a 340 one. That the extra MND does not always outweigh the secondary stats.
It's then up to the player's discretion to decide whether or not Vit/Pie are worth the hit to their stats.