Slagmaw the Slumbering

A card’s value diminishes the longer it takes to cash in on the mana spent. That’s why despite being a 20/20, the darkness never saw play.

4 mana is a major upfront cost. Aggro will immediately take advantage and pummel your face with damage as a result. To have to wait (up to) 8 turns, but more likely 3 or 4 is just too long for something that gets removed by a 1 mana spell and doesn’t heal in any way.

Would it be broken if Slagmaw had lifesteal? Maybe, but they definitely could’ve tried that, because you’re already paying 3 mana for an Execute + Excavate or pre-buff Shield Block (but Excavate instead of draw)