I can 100% disagree with this. As a person who farms content from time-to-time, I know that the most popular farms are the Bad farm and other similar farms which I will not mention. Without getting into too much with the working with AE, the structure of the most popular farms is Elite Boss spawns at lvl 1 or Bosses at lvl 1. Most of the farms were max number of Elite bosses and set to around 26-46 per map. So ... you didn't have giant spawns of mobs, instead you had maybe 46 individual spawns of Elite Bosses and maybe some Buff allys. The Warriors farm had larger groups, but still nothing compared to a Long Bow mission I just did last night on Red Side that was maxed to + anything x8. There were the same number of groups, each with about 15-20 mobs per group. So really, the most current AE farms, even the space crater farms (with large mobs) are about the same as a mission farm or actually a LOT less than the mission farms. I would say 46 elite bosses cause way less strain then 46 groups of 20 mobs.
You can disagree, and site specific missions, but that fact is that in general patrol and ambush AI causes more strain on the mapserver than standard idle AI. Leandro has already stated as much several announcements ago:
Zone and mission maps for all servers run all together in the same hardware (the ones described as "mapserver hosts"); so there's no such thing as running AE for "just one server" without affecting the rest. The AE farms trigger a lot of ambushes or AI-enabled patrols which use a lot of CPU power and cause increase lag and instability for everyone.
The goal here is to get the servers to a point where they don't need a restart every few hours.
The Bad Farm and the Warrior farm, as well as most of the other popular farms, didn't run a single instance of a "Patrol" or "Ambush" AI. My guess is that the Dev choice missions, the ones that were more story driven and promoted as better for the community, had lots of patrol and ambush AI. I know the farm missions didn't use patrol or ambush AI because I made some of them and recreted some for testing. So, although Leandro posted something regarding AE, it doesn't really apply to the most farmed missions. It would rather apply to the other more PVE story driven content.