Delta no longer publishes an award chart, but they do have regular award sales and there is generally a minimum flights will cost. It looks like the minimum a one way business class ticket to Europe has increased to 105,000 miles one way. Previously these flights would cost 86,000 miles, interestingly partner bookings with SkyMiles haven’t increased in price and still price out at 86,000 miles. In December 2017 Delta increased business class flights to 86,000 miles (from 70,000 miles) before reducing the price again only to then increase it back to 82,000 miles in June of 2018.
Part of the reason I hate the fact that Delta doesn’t publish an award chart is because they are able to make no notice changes like this. This is a significant devaluation and as loyalty members there is not much that can be done.
Hat tip to VFTW