Garrosh would have kept doing Mak'gora's against any leader who challenged him until no named chars were left since Blizzard wanted to keep the faction conflict going.
I know your an orc fanatic but everything we know implies Cairne would have won and his son easily tore Garrosh apart with his bare hands in the alt timeline. Sure Cairne was much older but the dude was already like 100 during the 3rd war and still easily fucked shit up.