Has anyone come across incident energy over 8 cal for a 30A 480V disconnect?

It can happen.

Since the arc duration is usually defined by how long it takes an upstream overcurrent device to clear the arcing current, a larger incident energy is often due to a longer clearing time from that device.

What device is upstream? Do you have a clearing time from the study result?

Easier than that if it's fed by one big transformer like say a 1000 kva.

we have it happen quite often in our Quarries. When you go 1500 feet of cable to a pump down in the pit the short circuit current goes low and the trip time on the Circuit breaker becomes long.

Typically happens at test switches or switches for power factor correction (or PQ monitoring) that are tapped off the main bus of 480 V switchgear. Why those switches are installed the way they are is another topic. As many have pointed out, it's what's upstream that matters.

The question would be more interesting if we discussed the possibility of exceeding 1.2 cal down stream from a 30A or 60A fuse and or breaker. For those that use arc flash software try and get the incident energy above 1.2 cal down stream from a Mersen A6K200R or Buss KTSR200.

That seems to be the case regardless of the make or model of device once you get down below about 150%.