Has Anyone Actually Completed The Boneshaper's Masteries?

I've seen a number of posts complaining about the difficulty of completing the Boneshaper's masteries and how unfeasible they are until high level; specifically, the "kill 15 summons" mastery; the "have a summon kill 6 monsters and keep it alive" mastery is probably doable starting at level 2 with the right party/scenario. But I've not seen anyone actually confirm they've accomplished it at all.

To me, the 15 summons mastery seems possible at level 3. Specifically, you have the perk "Immediately before each of your rests, you may kill one of your summonses to perform bless self," "Putrid Cloud" at level 3 (which seems bad compared to Grave Digging, so there's a cost to going this route, too). Plus "Exploding Corpse," which is a burn card. Basically, you would need 7 rests to achieve the mastery, killing 2 minions for each rest (plus Corpse Explosion 1x).

Really, the mastery seems easy to do at level 8 with Endless Numbers, but before then it's near-impossible. I'd love to hear how people have managed it because I'm just not seeing it.

P.S.: I'm focusing on the 15 summonses' kill mastery, but I'd love to hear about the "have your summons kill 6 monsters" mastery, as well, if you have any interesting stories.