Yes. You are correct. Sometimes client-side is better. However, currently http://jsblocks.com is under heavy load and is build using the jsblocks server-side rendering. The server-side rendering have caching enabled. I will introduce caching property that will update only the things like request to services which will help a lot.
You could take a look at the advantages here:
http://jsblocks.com/learn/introduction-why-jsblocks#server-side-rendering
Note: I have load tested http://jsblocks.com and it behavios extremely well.