I'd only salvage the perfect ones. I assume if people are wanting to buy a weapon upgrade x, they'd want a perfect (or near perfect) one. So there wouldn't be much point salvaging the ones far from perfect, except if you are wanting to use them later down the track (for yourself or for heroes).
Although I guess some upgrades may be in enough demand that people would want to buy non perfect ones of. Dunno which ones, trading in guild wars seems to be very tedious with no organized in game marketplace =/