Welcome to the Centrify forums.
Provided that your AD environment is healthy, you're using the correct version (for express users should be 5.4.2), you should not experience lag (unless you're talking about a very large AD infrastructure -that's what the licensed version is for-).
If I was you I would:
- Leave AD (using adleave)
- Make sure I'm running 5.4.2 (yum update CentrifyDC or yum install [rpm file]
- Undo all the changes you made to the centrifydc.conf and sshd configuration file.
- Join AD again and wait until the cache is built
- Try to login again and measure.
The post you referenced is not relevant (it is from 2012! product has changed too much since).
I would start there.
Note that if you're in an enterprise environment you should be using the licensed version (for very clear reasons).
R.P