Faerie Fire reads: “A troop afflicted with Faerie Fire will take 50% extra damage from damaging spell effects.”
I haven’t tested it with all kinds of damaging spell effects, but from what I understand the tool tip implies that FF should affect ALL damaging spell effects. That is not the case with life steal (Draakulis) while it is the case with Euryali (true damage).
Is this a bug? Error? Or is it somehow supposed to be so?