With a tainted blood pendant on, a mana tablet in my inventory, and the Greatest Band of Aura equipped, I don't get the Regen 2 buff. Tested it works with the Greater Band of Aura.

Likely caused by the IManaGivingItem class being deprecated from Botania.

Not reproducible. Do you use the latest version? And are there any other mods installed?

Running All The Mods 6. It looks to be working now. I don't think I was running on the latest version at the time. Thanks.