Looking at that screenshot, the high CPU is coming from the app. unicorns and sidekiq are all very high there. You can see that even htop is taking tons of CPU in that case. My guess is that you have some very bursty traffic headed your way.
Also looking at your machine running 7/8 unicorns seems overkill, I would maybe run 5 in your current setup otherwise there is very high risk of a thundering herd taking everyone down.
Can you include the expanded screenshot of detailed traffic reports? (bottom of dashboard)