Pirates in Vanilla are designed to be the 'rats' if you will - weak enemies for new characters to cut their teeth on. (D) variant ships are for the most part mediocre.
From what it sounds like, you are running Nexerilin, though I cannot tell what other mods you are probably running. Nexerilin does not make pirates more or less weak than their Vanilla counterparts. However as dk1332 mentioned, the Underworld mod pack adds more ships to the pirate arsenal and if you don't already have it I would highly recommend it.
(D) variants should not be less likely to be salvaged, but I do not have exact numbers to back this up.
For pirates, money generation is certainly more difficult compared to other factions. Have you already tried buying marines in decivilized locations and selling them elsewhere (decivilized locations include Maxios in the Magnec system and Killa in the Yma system)? Otherwise all I can suggest is smuggling in a hound, taking advantage of it's speed and small sensor sig.