My troops are invincible

So after 100% stealth cheese and Mind Crush spam I tried mass technicians. Turns out technicians/priests is just as good if not better than all the other OP combos. 3-5 technicians “ultimates” makes you immune to all damage. Enemies don’t even try to attack, they will walk in front of you and wait kindly for their inevitible demise. Use 3+ will heads to recover all the will points each turn.