http://gamerant.com/destiny-guide-weapon-part-farm/
Destiny: The Taken King is much more than a straight FPS. Its RPG elements mean players also have other factors to juggle, such as upgrading and inventory management. Currently in Destiny, many are feeling the pain of what some have dubbed “The Great Weapon Parts Famine of 2015.”
For some, this famine is hardly felt. But for others, even just a few Weapon Parts have become a precious and valued commodity. Ultimately, it depends on how each player makes their way through Destiny and (mainly) how he or she handles weapon upgrades. Here are some of the reasons why some players are hurting for parts:
Before The Taken King, reforging was all the rage. The concept was simple—reroll a weapon until it has perfect, god-like stats. Many players burned through tens if not hundreds of Motes and Weapon Parts searching for the flawless version of numerous weapons.
Reforging may now be gone, but another system, Infusion, has been introduced in The Taken King. Have an undesired weapon, but its Attack stat is above a current favorite? Just sacrifice that weapon into said favorite to beef up its stats. But doing so yields zero weapon parts, unlike the few gained from a straight dismantle. Some players only Infuse a very limited number of go-to weapons, while others desire a wide arsenal of upgraded and Infused higher-level guns. Since Infusion and upgrading costs Weapon Parts, the latter players are starting to run dry on Weapon Parts.
One of the few places to somewhat reliably farm Weapon Parts are the Strike playlists, but many players don’t spend much time there, instead spending their weekly time running the Nightfall, a few Heroic Strikes, the Raid, and Trials of Osiris (and possibly any extra “free” time in Crucible), resulting in those players earning a lower number of Weapon Parts.
Destiny Shadow Thief Strike Guide
Add to it that Patch 2.0.1 made getting Weapon Parts even harder with a 25% reduction to how many drop by dismantling weapons, and many are just scraping by. So for those Destiny players who are hurting for Weapon Parts, here are a few tips on how to get (and hold onto) more:
Strike Playlists
Strikes within the Strike Playlist have an increased drop rate on weapons. Almost all of them will be Rare/Blue, but they can be dismantled for Weapon Parts.
Return to the Prison of Elders
Remember that 25% reduction to Weapon Parts from dismantling? That only applies to Year Two weapons. If players can gather a cache of Year One weapons, the older higher drop rate applies. And Prison of Elders is the best place in the game to find Year One weapons in one place (It’s also a good place to farm Strange Coins, which also had its drop rates reduced in Patch 2.0.1). Just run the standard Level 28 Prison of Elders.
Stop Upgrading/Infusing Everything
If players can be a little more frugal and not upgrade and Infuse every single weapon in their inventory, it will go a long way in helping to preserve their overall number of Weapon Parts. The Taken King has been out long enough that most probably know what their go-to weapons are. Stick with those.
Check Alts
For those who have been playing mainly as one character since The Taken King released, check out those alternate characters to see if they have any Weapon Parts in their inventories. Transfer them on over to your main character.
It’s unknown whether Bungie will address any of the economy changes it made in Patch 2.0.1, but some are hoping they do. Granted, this isn’t an issue that affects the entire Destiny community, but it’s still worth addressing.
Here's my thing. They nerfed all hand cannons because of two guns in pvp. By doing that they killed them in pve. I would love to see the numbers on how many people play pve vs pvp.