8 isnt a overpay you are correct... he might be a top 32 defender, even though he is a top 10 scorer we all know and him too that thats because of the players he plays with... mainly hughes.
Here are some relevant comparables for Filip Hronek:
Mikhail Sergachev (Tampa Bay Lightning):
Contract: 8 years, $68 million
AAV: $8.5 million
Position: Left defense
Age when signed: 25
Thomas Chabot (Ottawa Senators):
Contract: 8 years, $64 million
AAV: $8 million
Position: Left defense
Age when signed: 23
Miro Heiskanen (Dallas Stars):
Contract: 8 years, $67.6 million
AAV: $8.45 million
Position: Defense
Age when signed: 21
Considering these comparables, an AAV of around $8 million to $8.5 million for an 8-year term would be reasonable for Filip Hronek.