As Tainted Flame becomes pure chaos, it seems that FoI has very few Vitality Decay sources. The “+100% Vitality Decay with +100% Increased Duration to Flames of Ignaffar” on Vampirris is useless now.
The Voidsoul Set is the only source of Vitality Decay. But for Voidsoul FoI, Vampirris is not the best weapon. Two MIs (Ugdenbog Flamestrife and Segarius’ Tainted Blade) and Blade of the Black Flame are better.
I suggest to change the modifiers to other skills. For Chaos FoI, we have so many weapon choices. For Vitality FoI, Decree of Malmouth is necessary. Vampirris is uncompetitive in neither Chaos Fol nor Vitality FoI.