I have the same MB with FX 6300 Black Edition and it doesn't overheat. I would suggest to take a look at your cooler. All in one water coolers aren't really the best as they advertise them
I only have a Cooler Master 212 EVO cooler with only one 120 mm fan and it doesn't overheat even when i render. Maybe your paste is dry or you maybe made some mistakes while installing you cooler. STILL ASRock MB are crap
If you can afford one , get those MSI MB cause they are great
Hope i helped you.