Throughput is degrading if backup primary is stopped

Build Info:
indy-node 1.6.565

Steps to Reproduce:
1. Install pool of 25 nodes.
2. Disable view changes and enable metrics.
3. Run load test ~100 NYMs/sec.
4. Stop the backup primary (1 instance for example) after 30 minutes.
5. Wait another 30 minutes and check throughput and latency metrics.

Actual Results:
Throughput is degraded and latency is dramatically increased if backup primary is stopped.

Expected Results:
Throughput and latency should be about the same with backup primary stopped.