Éramos nosotros los que llamamos a la puerta

Hola Colin

Yes, the structure used in that sentence is that, using the relative "los que..." referring to "nosotros". 

The explanation that both David and I gave using this other sentence that has the same meaning was to illustrate the similarity to the English "It was us the ones who..." = "Éramos nosotros lo que...", that means the same as "We were the ones who..."

You can drop "nosotros" indeed and say "éramos los que llamamos..." but in this case, the nature of this sentence is to "identify" someone doing an action, in which case the presence of "nosotros" makes sense. Even though you have the ending in the verb that already tells you "who" (éramos) the sentence seems incomplete without the pronoun.