I've never been around Grace, so I have no idea myself.
As for the other two, I've never been in a position to get a real read on Lockyer, but if he's coaching the right way for midfielders that would mean he's teaching things that he could never do himself [I just wasn't a fan of his play].
As for Ant Rocca, he underwhelmed me as a communicator with the players from the few times I've listened to him.
So, I find both of them somewhat questionable, particularly as they have both spent years and years in the same environment, although Rocca did start elsewhere.
Getting back to Grace, I believe that Simon Lloyd recommended him to us when he wanted to come back to Victoria, for what that's worth [Lloyd was definitely well-regarded by the Pies when he was here, if you don't remember him].