It's interesting that Randy was bitten by a regular one - it doesn't take a smart one to make a smart one, just need that one to already be smart, apparently. That info doesn't exactly help us to know what is going on with Datu.

However, what I think MIGHT be significant: Randy's eyes changed pretty much right away, if I heard that right. And if I recall, a big part of Michael's hesitancy to do anything to Datu was that his eyes were not yet changed. A smart one does not necessarily have to be a slow turner, which I guess I was assuming - their process would be different than normals'. Perhaps Datu will have the same kind of immunity as Tanya and Saul have shown?