I've lost count of how many juggernauts I've killed. Fortunately I counted a lot of them, so far up to 56 killed with no blueprint. That's less than a 0.3% chance to have NOT seen the blueprint drop.
I tried submitting a bug report ticket but was given the same copy/paste reply twice and was told to post about it here if I want to contact developers....
This is utterly ridiculous.
I see people have had the exact same issue and magically find a blueprint after they make a post here so here's hoping the magic response is a lot better than the support line (Sorry Jahn, you suck)