You will never get a good readout on your TPS on a dummy for a guardian, Defense or Hybrid. The reason being is that we generate addition focus for being attacked. This means in real fights you have more focus to spend on your high damage attacks. Also in the full defense spec each Slash lowers the CD on Combat Focus, therefore you can use this more often in a Defense build to generate more threat.
It's worth noting that Kitru is actually more correct about Riposte for Hybrid. In Hybrid, the stance generation is every 6 seconds. Riposte is 1 every 6 seconds so they offset each other in terms of Focus generated and used. You can have a look at threat generated from Riposte in a real world environment and add that onto a dummy parse to get a good idea of your TPS as a Hybrid Guardian. Full Defence on the other hand, your only viable (and still not accurate) option is to go pick a fight with a single Elite or Champion mob since stance generation is every 3 seconds and Courage makes a noticeable difference as Kitru mentioned.