@Shax
First up, you are discussing raid rewards. @sneeekypants has collected data on gear dropped from nodes.
Have you completed enough raids, recorded the results and compared to another user that has recorded their raid data in the same manner to show comprehensively that your raid rewards are statistically different to theirs? You will need to have completed approx 400 raids to get a statistically valid sample size, and even then your results will be subject to a 95% confidence level with a 5% margin of error.
Secondly, your information is based on the gear you still have in your inventory. I assume that a large number of players have furnace salvage in abundance. Does this mean that it drops more often? Maybe. But perhaps we need to factor in that crafting a furnace also requires an additional 70 purple salvage; salvage that is also needed for other gear or can be equipped alone. I'm sitting on 344 furnace salvage at the moment; however, if it didn't require any other gear to craft, I would be equipping a new furnace as soon as I had 50 salvage.
Finally, why is the dynamic drop rate theory being discarded by OP? I think this is answered by the comparing stats produced by various players that have actually tracked their gear drops. Sneeekypants states that cuff drop rate is ~20%. Other posts on reddit and this forum providing drop rates based on a statistically significant sample size also find a drop rate of ~20-23% for cuffs (10 node purples)
My own tracking of stun cuff farming: 359 out of 1562 pulls =~23%. This result indicates that I have a 95% confidence that the cuff drop rate is between 20.5 - 25.5%.
Therefore, the evidence from different players that have track their drop rates at different times but are still coming out with similar results would suggest that dynamic drop rates are not being used