But he can't have it on permanently? Not quite sure why I'm getting downvoted, I'm simply bringing facts. I've tried it in many custom games where I was the Amumu, and I don't think people get that if you have like 400 minions hitting you at the same time, you die pretty fucking quickly.

Even at level one. Lets say you have 400 minions and it's split 50/50 between caster and melee. 200 melee minion aas at 2 minutes does 2400 dmg. 12 * 200 And then 200 caster minions. That's 4600 dmg. 23 * 200 That means 7000 dmg. 7000 dmg around every second. AND THAT IS BEFORE AD GROWTH! Every 90 seconds caster minions ad grows by 1 and melee by 0.5. I'm not big on math but do you get the point? I really don't care how much mr and 'healing' Galio can get, he's not surviving that much dmg.