I never even had such a quest. Under Companions/Ifan in the log there was a subobjective called "Running with the Pack", which ended at the note saying "The hunt is on again." And another subobjective saying the same thing you mentioned, that Ifan delivered Death Fog. Does your journal say "The hunt is on again"? I might be wrong but there might have been some changes to the objective's name in a recent patch, and that might have messed with Malady's dialog. Or maybe there has been a bug in her dialog all along.
Either way, if Ifan was with you when you confronted Roost, you should be fine.
