Bizarrely, a town of less than four thousand people actually has an assassins' guild, with roughly ten members. Do they take turns, each assassinating one person a year?
The charitable interpretation might be that, in addition to being responsible for assassinations in the town, the guild is also responsible for assassinations in the surrounding countryside; in medieval times the rural population significantly outnumbered the urban population. (Also, a world with Raise Dead might be able to sustain a greater rate of assassinations per capital per year...)
But yes, plausibility gets distorted in favour of playability.
Well, Raise Dead is pretty pricey. And face it, nobody is out there paying to assassinate farmers. If you really want a particular farmer dead, ask some of the nearby lizardfolk to do it for a song.
Farmers are really interesting in the tax records, at least a function of property. They're the plankton of feudal society: necessary but otherwise nobody pays much attention to them. The miserable hamlets of D&D have an over-representation of every conceivable occupation but that of the farmer. Aside from being menaced by various low hit die creatures or being subject to the odd bout of lycanthropy, they're background figures only. Sad, but true.
> And face it, nobody is out there paying to assassinate farmers.
Ah, but in small towns essential services are often performed by volunteers. You've got your volunteer fire department, volunteer EMTs, volunteer assassin's guild, the usual.
In one of my campaign worlds the assassins guild was run by a church; you had to pay once to kill them, and again to make sure they stayed dead :P
Introducing magic, or any kind of efficient machine or analog for modern medicine that might appear as magic in a fantasy setting means you get to throw out most of the rules that are learned from historical observations, except where you base those lessons learned on post-industrial revolution studies where the availability of electricity and modern industrial tools haven't been made readily available to developing communities and countries.
Also an assassin guild may be paid to do it discretely - i.e. disappear someone rather than just kill. That would allow for more assassinations per year to go unnoticed.
The charitable interpretation might be that, in addition to being responsible for assassinations in the town, the guild is also responsible for assassinations in the surrounding countryside; in medieval times the rural population significantly outnumbered the urban population. (Also, a world with Raise Dead might be able to sustain a greater rate of assassinations per capital per year...)
But yes, plausibility gets distorted in favour of playability.