Though I am not sure on the execute myself even though it seems like a classic Warrior ability...Malth already has one and it is real poor. Maybe if it was instant it would be much better. I almost wanted to say Bladestorm because that is a iconic Warrior ability...but Samuro already has it.
I honestly don't think they will multiclass with Garrosh. We already have a warrior multiclass...Varian. I could see Blizzard making a druid multiclass, But two different warriors who is multiclass? What is the difference between them really? And honestly we have 3 warriors with Muradin which kind of fills the shock build.
I honestly see Blizzard making Garrosh the default 'Orc Warrior', which is why I was so pissed when they announced him as one. He was such a poor character. They will most likely make skins of other warriors like Saurfang and such on him...but it won't be the same...