defaults write NSGlobalDomain KeyRepeat -int 1
defaults write NSGlobalDomain InitialKeyRepeat -int 10
And turn off press and hold if you haven't: \
defaults write NSGlobalDomain ApplePressAndHoldEnabled -bool false
I can confirm they work because I am using these settings. Also make sure "slow keys" is disabled in System Preferences > Accessibility > Slow Keys.
Also, although it seems counterintuitive, I checked all my defaults for keyrepeat entries with
defaults read | grep -i 'keyrepeat' and found that I had "KeyRepeatEnabled = 0;" in my com.apple.Accessibility defaults.
So maybe setting that to 1 would override the other above defaults and prevent fast key repeat.
To match my setting you can use the command:
defaults write com.apple.Accessibility KeyRepeatEnabled -bool 0
You need to restart your computer for all of these things to take effect! Logging off and on did not change anything for me.