Google-sheets – Referencing a calculated value in another calculated value

Here's the general structure of my spreadsheet:

Start End   Count Duration Hours Count/Hour
09:00 10:00 10    01:00    1.00  10

Duration   = End - Start
Hours      = TIMEVALUE(Duration) * 24
Count/Hour = Count / Hours

Currently I use ARRAYFORMULAs in order to calculate Duration, Hours and Count/Hour for every row of the spreadsheet. It actually works pretty well but it doesn't seem like a clean solution. So I want to replace these ARRAYFORMULAs with a pivot table with calculated values.

I tried it and found that while the dynamic table is capable of calculating Duration it gives me an error when I reference Duration in the formula for Hours. It says the range is unknown.

Is it not possible to reference one calculated value in another? Seems like an odd restriction to have. The rest of the spreadsheet doesn't have this problem.

Is this possible in Google Sheets or should I keep using ARRAYFORMULAs?