I've been doing some empirical tests of Discipline spells to try to debug an Atonement simulator I've been writing. It keeps predicting that I should run OOM with the normal smite rotation after about 3.5min of steady casting. I've verified that when I stand around doing nothing that mana does indeed regenerate in game at the rate listed on the character sheet. I've also triple checked that my sim is accurately accounting for Evangelism, trinkets (Horridon's and 522 Valor), one mana pot (instant), Solace, Shadowfiend and Hymn of Hope. Rapture is not included, as both ingame and the sim I'm just running the standard Smite rotation.
...and yet ingame tests have me never dipping below 97% mana while actually spamming, and the combat log isn't showing any weird power gains. I've watched my own mana regenerate during the cast time of spells, and it's behaving like I have ~20k mp5. This is also consistent with my experience in raids; I noticed myself at max mana a lot after I switched to Solace mid-run.
Anyone know what's up with this?