Since the post was over 7 months ago...
The Demon Dogs didn't give extra EXP...his system went like this:
Round 1: Level 1-5 = EXP gained (for ease of calculation 2100x5 = 10,500)
Round 2: Level 1-5 = EXP gained 10,500 + hidden stats (EXP 10,500, I'm guessing level require goes up...