Ah, so all that is essentially an elaborate backup system. I too thought we'd see some Z up in the halls o' blending, but no they never got close to making it that far in.
I only have 2 blades so far, well also one under my drawbridge at my base, but on my BM tower only 2. They do make it to them, not often though, just the ones I or my turrets miss. Of course this increases with each BM, so we'll see how it holds up for later hordes.
I am going with a BM tower design I have used many times and evolved over many games. I've got it into a nice predictable state, ala Tower Defense style. The key isn't keeping them out, but giving them a clear way in, and meeting them there with all your firepower. Sure some still try to mow spikes and make another way in, but at this point in my design I can safely ignore those, for the most part. I can just flip a switch here or there and turn on perimeter turrets who take care of them if I'm busy. Getting some XP for trap kills now is so nice, even though it's lesser, it's so much better than nothing. I still only use them if A: I get overwhelmed or B: Get distracted(reload, repair, need to check other areas, etc.),
The tricky bit I found with turrets and such is placing the switches and other electric components in a safe spot where you can both reach them and keep them from getting spit on/destroyed. My first shotty turret was above my head, it was taken out early by a spitter aiming for me from below, now they're kept off to the side, little things like that I've tweaked over time.
One thing about your video though, in hindsight... where were the vultures? I don't remember you dealing with any, and if so not many, no where near as many as I tend to get, even in lighter hordes.
I casually play tons of TD games like most peeps play solitaire, this is the first FPS that has filled that niche/desire, which is neat. Last major one I played was They Are Billions... omg could you imagine that. Is pretty similar in ways, obviously horde size in that game is a bit bigger. Plus all the units, buildings, etc. I hope at some point they expand upon and add more to the Tower Defense aspect of 7DTD. Seen some neat ideas in here so far.