Overall those numbers sound low - irrespective of the Server version.
It sounds like you’re doing synchronous operations - which will never be the most efficient (you’re essentially benchmarking your network round-trip between the App server and CB Server).
Having said that, I wouldn’t expect a 30% drop (I’d expect it to be faster).
- What eviction policy (new in 3.x) are you using on the 4.6 cluster?
I’d recommend testing with the newer 2.x Java SDK also - particulary if you’re using async operations you should see a massive (order of magnitude) speedup.