My very first HC character just dinged 70 para lev 1, what level do HC start getting keys ?
Same as SC. You can find keywardens at Torment difficulties.
Note that, machine (key) drop is not guaranteed. The chance rises with difficulty level.
T1-3 is less than 100%. T4 is 100% and T5+ has chance of getting 2nd, 3rd or even 4th machine.
Ref: Diablo 3 Difficulty Overview
OK, thanks for the reply!