I'm extremely skeptical of a 17% case fatality rate (likely not death rate, which is different). That's almost certainly high due to under-reporting of cases. Iran's public health surveillance system is likely not as good as China, and they've not acted with the alacrity that the Chinese have.
But it doesn't have to be a 17% CFR rate to be a disaster. The Spanish Flu of 1918 just had around a 2-3% CFR, but it was easier to transmit than the common flu, so it spread quickly and lots of people died. Covid-19 appears to share the relatively high r0 of Spanish Flu. So there's ample reason to be concerned.
But it doesn't have to be a 17% CFR rate to be a disaster. The Spanish Flu of 1918 just had around a 2-3% CFR, but it was easier to transmit than the common flu, so it spread quickly and lots of people died. Covid-19 appears to share the relatively high r0 of Spanish Flu. So there's ample reason to be concerned.