BUG: Certain spells and abilities that are supposed to use BASE% power. i.e. without equipment/buff/RA use TOTAL% power
this was done in the frontier to ensure accuracy, I also concluded that +pie and +power is working correctly by using Twinkling Tiara charge and tinderboxes
In this test: my highlander paladin (83 base Piety at lvl 50) swapped between full +75 pie +26 power item set, and a test without equipment, mostly to ensure that +piety and +power was correctly increasing power pool. and by using Twinkling tiara charge and tinderboxes, I could confirm the item bonuses effected total power pool.
Oddly the ingame description reads 60% power pool for each spell, but was able to cast both at the same time, both with, and without full +piety and +power bonus from items.
This got me curious, and tested theurgist pets which are supposed to use BASE% power, the lvl 40 spell "Call Supreme Earth Elemental" 12% power delve, costed 7% total powerpool to cast a single one, both with, and without +75 Intellect +26 power item bonuses.
I hope this helps troubleshooting.