I don't have a moat around my new base but rely on kiting attacks away. There was a ground shake event when I was working on the fences. I began running around looking for the trolls. And looking.

No trolls ever appeared. I don't think I have that many workbenches, just enough to keep the fences repaired. Each one is inside its own kiosk to protect them from attackers and spaced as far apart as I can get them. The compound is huge and mobs spawn inside all the time. (These days, they get greeted by wolves. I'm taking down the interior fences.)

Hypothesis 1: I ran around so much that the spawning algorithm couldn't figure out where I was.

Hypothesis 2: idk. I don't think it was workbenches.