Though actually there were working class areas where the Nazis polled very well; the classic examples are the Erzgebirge and the Vogtland in Saxony, which were depressed rural-industrial (mostly textiles) regions, without much in the way of trade union strength or SPD organisation.* And as this was before the mechanisation of agriculture all of those little Lutheran villages in North Germany were full of agricultural labourers and many obviously voted Nazi.
*There was also strong KPD support in much of the area, giving 1930s election results a rather... apocalyptic look.
Is this just me, or does any one else find it ironic that
exactly the areas you mentioned are the strongest areas for the NPD today?