This synergy has been pointed out more than a few times recently, but so far, Mazirek, Kraul Death Priest has been understudy to Commander 2015 mate Meren of Clan Nel Toth and Shattergang Brothers' good friend, Prossh, Skyraider of Kher. The synergy with Prossh is fairly obvious, as Prossh loves to sacrifice creatures and Mazirek gives him quite an extra boost, effectively doubling his own ability while also benefitting any other creatures you may still have out. But the synergy with Shattergang Brothers appears to be even more obvious, as you're getting 2-4 sacrifices at a time in a typical multi-player Commander game. That's a lot of +1/+1 counters you're racking up all of a sudden.
Shattergang Brothers' decks have plenty of creatures and plenty of ways to make more on a consistent basis. It's just a matter of working Mazirek, Kraul Death Priest into the deck. I'm sure plenty of Shattergang Brothers lists will find a way to incorporate this very abuse-able pump ability in the near future. He's not one of the more popular Commanders in the game, but this combination could make the Goblin Brothers much more of a threat than ever before.