*UPDATE* Ok, for some weird reason Leatherworking Kit does not work with Encumbered Pack Mule they way I thought it would, the copy does not retain the handbuff. So I replaced it with Wolpertinger (which is better anyways as it summons 2 minions immediately AND works with the buff). There is also some synergy with Devouring Swarm in that Wolpertinger gives you back two cards instead of one due to the way the card copies itself on the board.
just wanted to share a swarmy combo deck I'm using right now to surprise some of my opponents. It works quite well, uses death/beast synergy and crushes control. Since technically you draw 6 beasts in total with Leatherworking Kit, there might be one Beast missing - still trying to figure out which one makes sense. But Leatherworking Kit definitely needs to be in that swarmy deck as for it to work a total of 18 minions have to die.