Yes, there's botting for resources in ESO that ZOS doesn't seem to notice. But that's not the only reason silk prices have gone down. One reason is that silk is relatively easy to get. Secondly, the current meta in PvP is heavy armor builds with very few light armor builds. So rubedite ore and it's alloy mats are selling for a lot right now. This will hopefully change after the next update when medium and light armor builds become more viable. As far as PvE goes, not a lot has changed, people may try new armor sets here and there, but once you have your set up finished, you're good to go. So armor mats don't get used up by PvE'er like PvPers do.
Resource sales run in cycles. When a new dlc drops, sales will go up because people are trying out the new armor sets, playing the new dlc and less people are farming mats. A few weeks before the new dlc comes out, sales are low because no one wants to waste mats on "old" armor sets, and are waiting on the new sets. People also are looking for bargains right now, so they wait.
(note, I never sell mats a few weeks before the new dlc, I wait to sell 'em until the dlc drops so I can get higher prices.)

lol boters I just sold several stacks and you know what I didn't charge the highest amount. I check see how much a stack of 200 or 100 goes for and adjust my prices to sell under 1000 to 2000 gold so that mine will sell I still make a nice profit. Only thing I have left that hasn't sold is 200 mats of raw jute.

Stop blaming bots and blame yourself for being greedy!

On EU PC rubedo leather, ruby ash wood and rubedite are 10-13 gold per unit while ancestor silk is 35-40 gold, 3-4x what the other cost. I'm talking about refined. I've done the maths using observed green/blue/purple/yellow temper drop rates and you barely break even if you buy unrefined and refine yourself, so I only rarely buy refined to make up for shortfalls when crafting daily writs since some months my surveys are a little skewed. But I am generally self reliant on base mats from those, hirelings and what I pick up along the road and have a healthy surplus when it comes to tempers. As far as I'm concerned. I haven't noticed any spectacular drop in prices lately. If I see something not selling at MM price within 10 days or so I check the trend and cut 10% of the price. I usually sell at -5-10% MM price at first listing because I need to keep my inventory clean. I mostly sell surplus items that are relatively cheap and only rarely sell materials such as tempers besides yellow and low-mid level base ones from daily writs if I have free slots.