Mint or any plants in the mint family grow very aggressively. It could choke out weaker plants.

i would never plant mint in ground without containing it again. It took me five years to weed out all the chocolate mint I planted. Mint is one of those " die hard", invasive plant.

Hmmmm... I have mine with Corsican mint and they're ok. Corsican mint isn't like most other mints though. Hopefully someone with additional experience can help you out to figure out why they're dying. Do you have any photos of the sick raspberries or of the site?

However much it spreads I can't believe Mint will kill your raspberries. There's something else going on.

If it's already an established bed of mint I could see it choking out newly planted raspberries. I wouldn't plant mint with anything (except other types of mint!)