err.. it's EB combined with horn that's op.. not minion eb himself. Don't really need replay to understand how it's OP.
1.) acquire large group of minions.
2.) Send them to attack tower .. activate horn when they are half dead. Watch tower die as your minions stay full hp
3.) Send them to harrass someone. If they stick around to fight, activate horn, watch them try to kill off your minions while your minions stay at full hp.
On top of this, you can do this while you're on the other side of the map.. shopping, farming another lane, w/e. As erabus, you can send about 18 minions that are indestructible for ~ 15 seconds (10 sec of horn of the battle.. but activate it when they are half dead ish) in the early-mid game. And they hurt. A lot. Nobody can do anything about them. At all. Stun them sure.. but the point is.. other people waste a lot of mana and time to try to fend them off yet in the end, the minions walk away full hp (unless it's liek reg drops mines and tb novas while the creeps stand in a ring of fire....). Even if they happen to die due to lots of mana and time by the opponent, you're regenerating more as creeps die around you wherever you are, and it takes 2 seconds to resummon all the rest.