The ability itself is fun, it encourages combat and sacrifice strategies, makes for great support for any archetype that benefits from your own creatures dying and it's, in my opinion, a good addition to the game
Cost reductions always useful in green, and decks that want this sort of effect could use more mana sinks
Sapphire ensures steady ramping, giving you the ink you need to fuel strong late-game plays, while Steel provides raw combat power to protect your questing characters and eliminate threats
These exile cards from the graveyard while doing other things
Whenever a land enters under your control, you add one mana of any color
While other resources are often co-dependent on synergistic cards or strategies, card draw is one of those few mechanics thats always good in a vacuum