if you use ur disc gear for the holy spec, then it’s probably a Problem of reforging and gemming and not that of a macro. Also using your mana reg skills (mindbender and hymn) at the right moments and using the right skills, not just spamming POH.
Even i still have mana Problems at very heal intense fights although every gem has Spirit. That’s the life of a holy ^^
Little advice: minor glyph “sha” removes the gcd of your mindbender so you can integrate it in macros, i.e. #showtooltip Mindbender
/cast Mindbender
/cast Circle of Healing
The glyph may be very useful in every spec.