That behavior could very well be the CPU boosting while its most needed. So, yeah, pretty much normal.
80C is a very average temperature during gaming and well within safety limits, so don't worry.
You could undervolt or curve optimize to get better temperatures. Also, set a better fan curve during those loads to help.
I'm not familiar with that brand of AIO, could be a weaker design....
Good luck.
The Englishman