You are capped acc for the content you are on. You can easily get the acc you need for second coils by swapping out gear options and gaining early drops and using food. Personally I wouldn't suggest spending on heavens eye IV for acc you don't need. Future content will come along with gear with higher acc with options for those who did not meld their weapon with acc.

There is some argument against capping parry as well. One being that the dps checks in second coils are pretty harsh and the extra crit/det would do more to help your group than having that damage mitigation. Going in to T6-7 I was surprised at how easy healing was. The stress seemed more on the dps to really push through for us. T8 was the first turn I felt the pressure in healing and the absolute need to upgrade my gear (as healer). The tank upgrades certainly helped as well.

TL;DR If I were going for curtana novus I would go crit/det/acc with nothing spent on materia IV.