Hi plz,
Make Wrathguards dual-wield again!
You can set the offhand weapon swing damage to 1 and the Main Hand swing damage to %Main Hand Swing Damage% - 1 and then you dont have to worry about balancing issues like you said you had.
Alternatively,
Add a node that gives Grimoire of Supremacy for Warlocks and then just add that and balance problems be damned!
One love!
Raxxy