Kontakt has very CPU expensive effects that instruments can use.  More often than not it's the instrument rather than Kontakt itself, since an instrument is a full on script. Kontakt's IR reverb is expensive and a few of the other effects are also costly.  Then there is all the scripting, which can easily be a problem.
 
If it's not the script/effects, then there is the memory issue.  Kontakt has some settings that control how much it loads of samples into RAM but instruments also have some control there.  If your are swaping due to low memory it can really effect performance and cause crazy CPU usage.  Each instrument in Kontakt will show how much ram it is using.  It wouldn't take much with 23 instances to blow that ram budget. 
 
If you are loading multiple copies of the exact same instrument you should load them all in a single Kontakt instance, since they can share the sample memory.  If however every instrument has its own separate samples, multiple instances of Kontakt are better for CPU loading.
 
if your signature is correct and you only have 16GB of RAM, I'd take a hard look at that.  I'd say you need at least twice that much RAM to do anything I'd consider a massive orchestral template.

It may not be Kontakt if you have an AV that is persistently scanning files as they are loaded. That would cause a lot of overhead as Kontakt tries to load the samples. Not all AV software is smart enough to ignore samples.
 
Regards,
Dan

Before SPLAT incorporated load balancing Kontakt used to hit my first CPU core pretty hard especially on the Abbey Road Drums. As msorrels says the effects within the specific libraries can really take up a lot of cycles. There are many times on bigger projects where I will bypass the Kontakt effects and just use SONAR effects. That has helped a lot.
 

I don't think load balancing works with synths today.

It works with a lot of my CPU hungry stuff. load balancing has helped with Kontakt and the Arturia collection for me, but I'm on an i7.
 

emwhy
It works with a lot of my CPU hungry stuff. load balancing has helped with Kontakt and the Arturia collection for me, but I'm on an i7.
 

I don't think it works with Synths, unless they are in an FX bin.
 
"When enabled, SONAR will attempt to load balance FX Racks that contain two or more unbypassed plug-in effects, including track FX Racks, bus FX Racks, clip FX Racks, FX Chains, ProChannel FX Racks, and ProChannel FX Chains."