I'll say this......
....back in school I was the ONLY Austin fan at first in 96, and then later the ONLY Rock fan in late 97.....why? Because I saw before everyone else I knew, that those guys had "it". Several months later, everyone else jumped on the wagon
Barring anything weird happening, Reigns willl be a star. A big star, but to my eyes, he tops out at level slightly bigger than Batista, but below Cena. He won't be the face of company like a Austin or Rock though. I dont see it.
Far as his mic skills, I don't know that he'll be the jokey, upbeat charismatic character of a Rock or HBK. But maybe he's a funny guy off camera.... given time tho, I think he'll get good enough to where it's not a hinderance.