I think I had it at level 32, if you're looking at logs. Though most of the time I played Adekar I had so many other Fortress people on that there weren't many people to kill unless they were going to be ganked.

But really, if you're a Maran and your main objective is to pk, why wouldn't you want to take an edge that increases the level of your best servitor for doing so?

I didn't write nor have I looked at any of the code for conjurers or these edges, but I think there's a fair amount of weird superstition surrounding conjuring.

Certainly there's an opportunity cost to pay in terms of downtime, but more mana and higher level is always better (unless you're pretty sure they're going to turn on you).