Have you guys came across terminals yet? I am still playing the campaign and when I'm done I'll start looking for them. Currently I am on The Maw on heroic. The only terminal I came across is on Truth and Reconciliation. It is in the bridge of the covenant cruiser. Just hold (X) on the the ship's screen.
Maybe you can share if you found them where to find them.
Also, I haven't found any skulls yet