As an Earth player, I can safely tell you that it's by no means invincible, especially because your defense is only as strong as your staging area, but that's a good thing, since Earth would be unbalanced if it were impenetrable. That being said, I'm pretty confident in my defense most of the time, though committing and destruction do give it a bit of a hard time.
Is Earth Invincible?
Wafflecopter said:
I think Blinding Rage could only tutor for 1 of the foundations that was destroyed by Infiltrating, because they're all destroyed at the same time (Blinding Rage gets 1 chance to trigger after your choice of foundations explodes, but then its no longer in play)
This strategy entirely fails to work against Fire.