So at 85 my Penance, on my horde, is 3,100 mana and heals for roughly 11k a tick. Flash heal is 5,900 and heals for 28k, greater is 5,900 mp and heals for 38k. PW shield absorbs 50k damage in my last tier 397’s. Aegis absorbs 58k. Spirit shell absorbs about 83k.
At 86 Penance is about 4,500 mana but heals for the same, flash heal is 7k mana and heals for 29k, greater is 7k and heals for 39k. Spirit shell absorbs 98k. DA is 68k. So this is about where the mana pain comes in. Sigh.