This card is too cheap for such versatility.
Let's take simple combination: Magical steel > Divine guidance with 20B/11G/20R. Turn 1: +10R, -6G. Turn 2: +7R (or +10 wall), +10G, -5G. Total income: 10R/10G/10 wall or 17R/10G for 11G. And I can play this combination very, VERY fast - I need 1 round with standard production to start it and 2 to play it with guarantee. 2-3 turns more - and here's Orc regiment for you.
But even without Restoration keyword this card is really good.
Round 1 - +8R from Colonialism. Round 3 - +7R from Divine guidance. Round 5 - +20R and a hand from Revolt. Round 7 - something with a ton of attack, you'll be able to play it with your 54R. Round 9 - destruction victory, Assassin award. It's kinda ideal scenario, but real ones don't differ really much.
10 wall for 5 gems is not bad either. In normal games this amount of wall is pretty much a difference between life and death. Why should I take Double wall or Reinforced wall instead of Divine guidance?
I think that Divine guidance needs higher cost. 7 or 8 gems. It won't solve Revolt problem (cause recruit gain from Revolt should be lowered), but fast Restoration combo will be harder to play.