Why is it particularly good in a monosphere deck? If the resources have to come from a single hero (which seems like an unnecessary restriction from a 'just ok' card), why would monosphere help out?
In a multi-sphere deck, you might need your Leadership resources for other cards like Campfire Tales, Sneak Attack, or Errand-Rider. Makes it hard to save up 4 resources on your Leadership hero. But in monosphere Leadership (or even dual-sphere with 2 Leadership heroes and 1 hero from a different sphere), it's a lot easier to save up 4 resources on one hero while still paying for those clutch Leadership cards with your other Leadership hero(es).