The build is nice overally. Well, all of them, actually. I just want to state that after playing him with Liandry a few times, I realized that item is not really useful on him. The problem with the item is, its passive is not useful to AP Amumu (no time to apply it effectively, he is rather bursty), its stats are neither gold-effective (80% only) nor slot-effective (low AP, low HP stats).

I saw it only in one of your builds and I think it's still one too many. The item is totally not worth it on Amumu, where its component Haunting Guise might be useful early, but it should be sold later with a loss of 445 g when you need more room (same as with Brutalizer before BC was remade). Anyway, I think a Rabadon is much better idea in any situation while Liandry is a poor choice.

The only Amumu I'd possibly build Liandry on would be a tanky Amumu with only Rylai and Liandry for AP (the rest being tank items, e.g. Sunfire, Frozen heart, Warmog, Banshee or Thornmail ...). As a tanky mummy, you will probably not burst anyone to death with just your combo, however, you can cry all the day long and apply the passive more thoroughly.