From what I can tell, you need to re-do the Purge and detection.
Can you redo the test, but drop the Battery & Omnisphere (and everything else)? They might scew the test result. It would be interesting to know what results you get with only Kontakt.
Another interesting question is what computer you use. From your description I would guess that it’s a 15-inch 2.4GHz PowerBook Pro with Retina display. If that is correct, that processor is quad-core so you should be able to detect a difference.
Furthermore, of case you will see that 12 instances of Kontakt than with one. That is not the main issue, though. Cubases meter only shows the overall power use. What is interesting is how much the individual cores use! There are utilities that can measure this (but can’t recall a name right now). If you task one core with handling all your 12 instances (equivalent), it would be overloaded (resulting in droputs, click and pops. As well as crashes) as opposed to spreading the work over all four cores.
Using the VST Instruments Rack option, you run the risk of overloading 1 core, while the other 3 are running more or less idle. In this case, the Cubase processor meter would still tell you that you have plenty of power left!