According to the in-game description of the Ancient Knowledge passive (Destruction Staff skill line), wielding a Flame Staff while having a Destruction Staff ability slotted will increase the damage of your single target abilities by 8%.
Checking the tooltip damage of the Greater Storm Atronach ultimate (Sorcerer class) while wielding a Flame Staff, the "Atronach Zap" attack appears to be affected by Ancient Knowledge as shown below.


Casting the skill on a dummy, however, results in the damage from "Atronach Zap" being the same whether the Ancient Knowledge passive is active or not.


Whether this is a visual bug (the tooltip should not change when Ancient Knowledge becomes active) or a scaling bug (Ancient knowledge is supposed to apply to the "Atronach Zap", but it doesn't), something is not right.
EDIT:
it seems that all pets are affected by this bug, the morphs tested were Summon Volatile Familiar and Summon Twilight Tormentor, the damage tooltips of the pets' normal attacks change when Ancient Knowledge is applied, but the damage of the pets on dummy is unchanged (again, a Flame Staff was used as the pets' attacks appear to be considered single target damage).
Note: the damage pulse from activating Summon Volatile Familiar while the pet is summoned scales with Ancient Knowledge as intended, both in tooltip and dummy test.
Should anyone obtain different results, please share them.
Edited by PK44 on February 18, 2018 7:22PM