Sounds like mesh/shimming might be a tad off?
If your running 7.4v then 22rps does sound about right, my krink build has the same setup (12:1 standard warhead) and puts out 18rps although granted its being fed with nuprol batteries.
The thing with the warheads isnt the top end speed but the pickup, so whilst auto might not be much to write home about the semi response is fantastic if you have a ton of precocking.
Edit- just seen thats 11.1v, yeah defo check the shimming/pinion mesh