I really do think Bispings accent does hurt his communication because as he gets more excited and tries to give any detail you kind of have to decipher what he says. Really he should have one of his assistant coaches giving the advice, but he can tell the coach what to say.
Miller seems to not only be training well, but he starts using a certain terminology, like the choke, and he yelled for that specific choke during the fight. It is details like that which make even a bigger difference. Also he gives a lot of positive reinforcement in the simple statements like "GOOD!" where Bisping just yells at them to do something or get up.