This is your 22nd novel, and I've read all 22 over the past 13 years. I'd like to say I've enjoyed them all, but somewhere around the 15th volume, your books became a bit of a slog. I think I've figured out what your problem is - you're putting Baldwin and Simon in too broad of a context. For 15 books, you had them solving local mysteries - the external world of the 14th Century might be mentioned but had little if any effect on the matter at hand. Then you sent your detectives on pilgrimage - an interesting plot device, but not one that worked particularly well. Still, it was less distracting than your recent habit of injecting the political intrigue of the 1320s into Dartmoor. Yes, the battles between Isabella and Edward II and his lovers are intriguing, but they feel tacked on when they affect a local baron and his friend the bailiff. Alison Weir's biography of Isabella was fascinating and your series takes place while she was in power, but that doesn't mean you have to tie her into your plots.
It's sad, because there are some good parts to The Malice of Unnatural Death, and the idea of a necromancer attempting to murder long-distance is fascinating. You've tied this quite well to the subplot concerning the order of succession at a local abbey, and Coroner Richard's booming personality is more amusing than distracting this time around. You've finally figured out the right tone for that character, and I now look forward to seeing him again. All you need to do is trim about 50 pages of obfuscation and keep the bulk of your story local. A good editor can help you do this - perhaps it's time to find a new one.