I used this build against a havy ap team with nidalee, veigar, zac, brand and lucian. I bought the items this way so I would be unkillable in the late game due to 1. zhonyas 2. GA 3. my ultimate 4. all the tanky stats given by the items in the build. Besides the armor, mr and health, these items also give a decent amount of ap + basic damage (bami cinder).

As ekko with this build you want to push as much as you can in top lane. Rush your zz'rot and place it under your tower. When its activated you are free to roam while it is pushing and farming your lane out. With banner of command these waves get even more annoying...

In the late game you have to make sure you are sticking to the enemy adc in teamfights get your stacks on them and try to peel for your carries by using your parallel convergence on as much people as you can. A good ultimate can turn around a bad game despite the little amount of ap you have.