It was not easy to get enough poison to kill hundreds. You get some hemlock, dump it in a well, and it dilutes enough that a dozen people get stomach aches and one elderly person dies. It's feasible to pull this off on a larger scale, but you'd need a lot of poison, and therefore a lot of resources.

Fires? I'm not sure it was that easy to set an out of control fire that would consume enough of a town to kill hundreds. Does everyone just fail to notice as you splash pitch on buildings all day leading up to the final act of starting the fire at night?