Hoyas often have small roots, on relatively large plants. This is normal, I think.

It's interesting that here's what you said: "when I look at the root ball, due to lack of growth, it looks ok but small and not vigorous."

The thing is, you are not looking at ones that do grow nicely - you may find that they still have small root balls.

H. deykeae grows slowly for a lot of people. And it's very fussy, too.

Thanks for the information. You are absolutely right. I shouldn't impose my impatience on my Hoya plants. Go with the flow, so to speak.