Amusing trick.

[Executor]

That's just the 'refuses to use gems because the enemy is too weak' problem, isn't it?

And a mighty problem it is when you lose a Seraph with 150 gems of equipment to 180 gold shadow seer.
But I'm not sure if it's a "too week enemy problem", I know infernal disease is a good way to use up gems on some commanders since they do cast scripted orders, like rain of stones or whatever.
That can come in handy very much.