Some handy things about the powered spawner: by default it behaves as a spawner and I don't think you get much control over where the mobs spawn. If you want to build an easy grinder then you might try running it in "capture" mode instead.

In capture mode you supply an empty soul vial and it puts the mob in the vial instead of spawning it. This combines quite well with the autonomous activator. Using the activator gives you precise control over where the mob appears.

In the picture the spawner is configured with its "pull" side facing the spawner, this saves you having to configure a servo and/or filter. The push side outputs into itemduct. In this example I've used fluctuating itemduct so it also supplies power.

ONLY PUT IN ONE VIAL, if the filled vials stack they cannot be right-clicked meaning the activator will jam.

As far as I can tell the autonomous activator will not auto-eject. It doesn't appear to recognise the augment.

If the COFH wiki is right it might be possible to put the spawner next to an unmarked side of the activator and set the spawner to push and pull directly, eliminating the need for the duct, but I could not get that to work.

handy, but i just use a mob atractor to pull the mobs infront of my killing machine.

In CC you can simplify this. The activator can be configured with a neutral side, a small black square which appears to allow push and pull.

The spawner can be configured with a single "in and out" side, avoiding the need for the side duct.

Now I just need to set up an auto-shutoff to detect when my killer-joe runs out of swords or nutrient ... or maybe just a mob counter?

Oh BTW:

It isn't always made clear that the killer joe needs at least 1.5 buckets of nutrient to run but a maximum capacity of 2 buckets, meaning it needs a way to top-up by half a bucket.

Incidentally it can be set to pull and push liquids, I was able to configure the top as input then put a drum of nutrient on top. This largely solves the topping up problem.

It also looks as if the vat goes on consuming supplies even if its output tank is full. It has an annoying tendancy to produce fractional amounts not whole buckets.

Other things: Killer Joe won't accept Tinkers construct weapons, but will accept a fluxed sword. The fluxed sword will recharge from a wireless charger, so it won't wear out. I haven't tested the fluxed sword in an autonomous activator yet.

Also the powered spawner seems to only ever make small slimes.