I don't know about declining, but no one likes change unless it is a massive benefit to you personally (like no fees for private sellers-we responded well to that)

I adjusted prices to take into account the BPF (i swallowed about half of it) and sales slowed, but what I noticed most was the items which sold had been on for a long time, they had been regularly refreshed but often got no views previously.

I refreshed all items with no views, i got a massive amount of views, sales not so much, but were ok.

I added postage to all items instead of free post in preparation for SD and didn't adjust the price of anything. Didn't even do a sell similar refresh, views go up, sales unaffected. Still ok, and probably not bad for April. 

My theory is that there are a lot of changes to search algorithms which we are not aware of. It doesn't matter what you do, do something and views will improve and sales are ok. JMO