Stratum pool has to use extranonce2 size 3 or higher. Minimal pool difficulty is 16 (0.001 for X11 and X13).
We had to change this, because some pools were using difficulty 1 regardless of hashing speed being sent towards them causing very high load on our servers thus bad performance. Every decent pool gives you ability to configure worker difficulty, so make sure you configure higher diff (we recommend at least 4096 or more).
I had minimum difficulty set at 1024. I increased it to 4196. Still seems dead. What pool does nicehash think works best with its service? (don't say ghash.io)