I'm serious: Bloodmage silver isn't so bad. Once Lujo does it once he'll be complaining about how easy/broken it is.
Having said that, I'm not sure that it's supposed to be the way it is. There's no way you can possibly take out his first form using magic. There are just too many plants. Goblin + bear mace is the way to go.
Thief silver is much harder, methinks. And I think most golds are impossible.