Mana regenerative nerf after 3rd ascendency...

I recently got my 3rd ascendency on my lvl 79 monk. I chose to get 12% mana leech and mana leech is instant. Ive changed nothing else with my character, and before, rarely used a mana potion. But now that I have my 3rd ascendency, I have to use my mana potions every 5-10 seconds while in battle. I got the mana leech to minimize mana potion use, and now I'm using them more than I ever have. What gives?

Update, I changed my 3rd ascendency to chaos damage, and my mana regen and leech is way better.
Id love if my mana leech/regen was 12% better and instantaneous