[ano]

It is not an advantage because you are short of maneuver. If the enemy decides to attack you in magic phase you may do nothing other than accept the fight. And be killed in most cases.
You can't script retreat for a mindless commander and that is the biggest problem.

Also, I'm not a fan of marble oracles because they have the same problem though they are quite tough and hard to kill. But still I once killed 3 or 4 with a Djinn and they could do absolutely nothing. A huge waste of gems.
But marble oracle has 16 MR while Crusher and Gargoyle have 12 which means they are very vulnerable to something like opposition and, again, you can't do anything with that.
It's up to you, of course, but a good player will beat it easily.