OK, I’m back at base now and can give a bit more of an informed answer…
Yes, looks like the ds18b20 can do anywhere from 60 to 120 usec per bit. The uart offload solution I use uses a bit time of 87 usecs (uart set to 115200 baud and each uart byte representing one OneWire bit) which explains why mine is coming in a bit slower than your calculations.
And I think that assumes only one sensor per bus. If you’ve got multiple sensors per bus then 2 request bytes becomes 10 request bytes because you need to include the ROM code of the device whose scratchpad you want to read. There’s a pic of that here. Using my timings that takes ~13 msecs (not including the reset). The Green and Yellow traces are two different OneWire buses running simultaneously.
Were you able to find it anywhere?