I think I am going to change a bit of what the master minions buff.. or at least add to the buffs.
Each master minion casts a buff upon the friendly minions, right now they consist of (at 15 skill points invested):
25% Attack speed and 20% movement speed bonus.
50% damage bonus.
Health to Master on hitting enemies.
Each of these minion masters will soon be adding a 10% DR buff at 10 skill points, and a 25% DR buff at 15 skill points.
Having all 3 Master minions means having all your minions at 75% DR as well as their other buffs.