How to change just the Dock hide duration?
You can change two values for the Dock when it comes to the animation speed:

autohide-delay

# Dock autohide delay set to 0 seconds, the default should be around 1.0
defaults write com.apple.dock autohide-delay -float 0




autohide-time-modifier

# Dock animation duration to show/hide the Dock
defaults write com.apple.dock autohide-time-modifier -float 0




Set the first value to 0 and the second to 1.0 in order to achieve your result. It's not possible, however, to set separate durations for the hide delay and the show delay.