Nicehash high pool rejection rate
### Description

Using the latest version to run a small pool. A few people use Nicehash under a single worker, so sometimes the worker has 50 ~ 100 times hash power than a real miner.  They got high pool rejection rate (10 ~ 20%) from Nicehash's connection report.

I'm planning to set up a dedicated port for Nicehash connections. In such case, what would be the good values for parameters like:
-    "blockRefreshInterval": 1000,
-    "jobRebroadcastTimeout": 60,
-    "clientConnectionTimeout": 600,
-    "varDiff": {
                    "minDiff": 1,
                    "targetTime": 15,
                    "retargetTime": 30,
                    "variancePercent": 30
          }

Any suggestions or thoughts would be appreciated. 
