Update Primary Servers Only?

I'm currently on 11.2 and am looking into upgrading to 11.2.2. I realize there are client side fixes, but are there any benefits to only updating the primaries? With over 4000 devices, we don't like doing any mass updates unless we have to. If I can update the servers and get 50 percent of the benefit with minimal effort, than to me it's a no-brainer. So assuming I can, is there any way to tell which enhancement/bug fix will be fully implemented with only the server side patched?

-Tim