After the tyrannis expansion, the loot drop from L4 missions has become significantly worse. Recently, I spent over an hour tabulating the salvage I had in stock, and what kind of profit I could make manufacturing and selling t1 rigs. In every case, I found I was making a loss or marginal profits. Am I missing something, or is it now NOT worth your time looting/salvaging L4 missions if you can run them fairly quick? I do have a single tractor beam on my PVE ship that I use for grabbing some looting while killing ships, but stopped bothering to show up in a dedicated salvaging destroyer. I even abandon my wrecks to make it easier for ninja salvagers.
Sam
I'd say salvaging is certainly worthwhile primarily for newer players. Once you can run level 4's relatively fast, it quickly loses its worth as you generally stand to make more money by moving on to the next mission asap.
For a lowbie player, the 10-20m you can make an hour is certainly worth while.
The consensus appears to be 1. definitely worth it for newer players 2. focus on large and (maybe) medium wrecks. 3. angel wrecks give better salvage 4. keep an eye out for t1 named items in the loot.