If the goal here is to make the revenant weapons more common and avoid a peg crystal situation, I think the drop rate would need to be drastically increased. It's so rare that a 20% buff even really doesn't move the needle.
The Rev table has a ton of alchables. Maybe you could cut down on or remove those, and in turn put the weapons at a reasonable rarity? Or even better, give it a reasonable rarity when your slayer task is revenants. Something like 1/1000 from the good level revenants on task, 1/500 if skulled?
Edit: Actually, could the skull mechanic be outright replaced by having a slayer task instead? It feels a bit weird to give such heavy incentive for skulling, when skulling is usually there to give risk to the pker.