The last few seasons of Death in Paradise really dropped off for me, personally it was pretty unwatchable compared to the first 3 DIs, now I'm moved on to other Brit Murder series and Beyond Death in Paradise, Faye most likely agrees :D
They def got weaker as they went. I do like Humphrey which is why Beyond Death in Paradise is pretty good, plus it's a current show i think they release the new episodes on Thursday so can't binge them all and be stuck in a couple weeks. Morse / Lewis / Endevour were all good series and Midsomer's Murders as well if you haven't seen them.