Not at all. Temperatures of 80C won't cause throttling, and can be run perfectly fine for a long time, but lower is better. Those temperatures are really good, you aren't seeing bottlenecking- and lots of AIO coolers can peform at those temperatures on full load. I hit about 75 on my cpu air cooled heavily overclocked on full load. I would overclock that cpu if you are noticing dips so you get better framerates overall, but it is not the temperatures causing them. The cpu is built to withstand temperatures of up to 100C, so you are more than ok. If you want help overclocking just pm me. You could undervolt the cpu to get better temperatures, by just taking the voltage down until it is unstable, then increasing it, but you aren't noticing problems due to the temps.
What might be causing the dips is the gpu- how much vram do you have, if it is too low you will struggle to run the game properly.
You also can consider that ivy was quite a hot chip, due to dodgy thermal paste on the cpu die. You can delid a chip and replace it, but that is dangerous and not advised.