For time, just know your enemies attack patterns, as some can stop you from hitting them. Get in close at all times, and with the obliterator gauge, keep using heavy attacks to distrupt thier attacks. Pound them quick but not too quick that you could miss out on valuable points. Remember, even if burst is full, keep attacking a little more to boost your ratings.
Its a great DLC from start to end, so just go for it and have fun.