The new "arctic fur" is a pain in the ass now. They nerfed the drop rate so its harder to get. My best bet would be to find a area or profile that goes through alot of mobs that are skinable and grind like a madman ).
The only factor the drop rate depends on is mobs per hour so to speak, not the specific mobs. Maybe elites or dungeon bosses might have a higher chance to skin for those things but the bot can't quite grind on that can it?