This volume is definitely suffering because of what you listed. On top of Spider-Man/Deadpool, Merc$, the ongoing minis, and Uncanny Avengers.. people are starting to get tired again. Mercs is ending and Wade's going to leave UA at some point, so hopefully there's some housekeeping going on with the Deadpool books... because a 6k drop is sort of alarming. And that's not the first time this happened with this volume.
True true
I should add :
additional costs
i think that almost all months have additional costs
crossover right now(i don't but all these series so i need to buy more)
MU special issue - january
deadpool 30 - 80 pages special issue and double shipping in the same month(one month after crossover)