Me personally, I salvage everything. Even blue weapons, purple weapons, and gold weapons (depending on what they are). I don't visit the Merchant unless I need a Kit. When it comes to gold salvage items, I'll check the rune first at the rune trader. If it's a good one (Sup Vigor etc), then sell it for the extra cash if you need it. If it's a Sup Rune of <attribute>, I'll usually Salvage it off and put it on a hero that needs it. Then Salvage the rest of the Salvage item.
I usually always get rare mats from gold Salvage items. Plus I like having an overstock of materials whenever I need them.