Okay, so this is the reason why I said there were 4-ish relics for this build. I actually used primal instinct for a bit and it's kinda hard to talk about.
This relic isn't for this build; I don't think so at least. When I was testing this I decided that having all of my permanent pets out as well as 6 swarmlings, just wasn't great in terms of pathing. Instead I decided to not summon my permanent pets at all and just spam GV, DS and BP over and over to spawn these little guys.
They're decently strong and actually kind of fun to use, but I say they're not for this build for a number of reason. The first is one I kind of mentioned already, that having other pets out can make it a pain, meaning that maxing out my summon skills is pointless.
These guys also don't have access to celestial powers making 4 of my constellations useless too.
I suppose you could take the points out of the summon points and put them somewhere else like Mogdrogen's Pact, Possession and/or Wendigo Totem. And the extra devotion points could be used for more defensive constellations like the Scales of Ulcama or Crane.
Basically, all I can say is that this doesn't suck as much as it doesn't fit this particular pet build.