I don't think bonfires count as base defense. I have had trolls spawn in front of them and walk right over them too, very funny except his log did some damage.

What I do and successfully maintain very large bases is pretty simple. First I ck that I am going only in cardinal directions with my ditches. The game makes ditches and earthen walls look awful unless they are going N,S,E,W. I dig down maybe four whacks w my trusty antler pickaxe as these bases are done as soon as I get it. Use better pick for plains farm.
Then inside and right at the edge of the ditch I use the hoe to go up 4 levels. That way the wall is too high for anything to pop over cept the flyers. Lookin at you blobs. Your first wall and ditch may be a bit wonky looking but soon you will understand how to make them look perfect. If one side has a good view I only make ditches, two of them with small walking area between, each a bit deeper than if I had a wall. They work great for the hordes as the berzerkers walk down and get pathed into the outer ditch where you can just ignore them.
Log trolls do damage to anything about three squares in except plants n trees so my garden rings the base. Then I set down workbenches along the perimeter then pretend I am going to set down a small building piece to light up any areas that lack coverage. Gotta be diligent so pay attention. A sloppy Viking gets neighbors comin in to do a little mischief.
The last step is to house all the workbenches in nice little houses, totally enclosed.
Voila. A well defended base. And my bases are big, bigger than the red circle. Yes it takes time, yes it takes mats, but I only have to mess with it once.