If a game is gonna last long enough to get the full effect from everything, I would go for a completely different build. I made 25k gold in one of my recent games with Amumu and it turned out to be the most insane tank build and best game I have ever had with him at 38/8. You don't have very much armor or magic resist as already stated. Remember, HP isn't everything. I once (with Malzahar) dropped a healthstacked Cho'Gath with little defence (about equal health, 4.5-5k) in no more than 6 seconds.

Leviathan is unessecary along with Warmog's. And dodge for Amumu slows down the spammable Tantrum. Instead, get Thornmail to punish them in multiple ways for hitting you. Force of Nature depending on the enemy team, or Abyssal if you want AP to go with magic resist.

RoA with Amumu... just no. Unless you are going for DPS and get it early. But Archangel's is better to build for AP. If you want more damage output, get AP and Mpen runes instead of dodge.

And a note on your team fight playstyle. As a tank, you shouldn't have to Flash out and reheal and then Teleport to join the fight again. By that time your allies are dead because your DPS/Carries are all squishy. That's what defence is for, so you can stay.

With the 38/8 game I mentioned, I scored a triple kill and picked up a fourth immediately after while standing in the enemy base with a turret beating down on me. Only one SFC and absolutely no AP items. The defence just let me stay alive long enough to AoE them down to ashes (which surprisingly didn't take long).



Aditionally, I could see this build doing relatively well as healthstacked DPS, but not as tank (hence previous steatements).

A lot of life is pointless if you don't have good armour and magic resistence to go with it. I've made a guide for amumu and I usually get somewhere between 10-20/3-6/20-30. Give it a look for some ideas.

Rod of Ages as last item probably. Takes 30 min to "charge up" so its a pure waste if you take it as last item.
Also Leviathan could be made a bit earlier or not made at all, for cost of another sunfire.

I could see this working in an hour long 5v5...