TB indeed diversity is beautiful thing but so is present "by the book" acknowledge where the classical case is discussed as a rule of thumb. Only in forums like this one expects to see lot of variations in responses.
Coming back to my original question, parallel connections in my cases doesn't seem to improve server response time which theoretically speaking isn't having parallel performance impact.
The time between GER request and ack are in miliseconds. To give more context the server is acting as reverse proxy with modsec rules turned on. It's WAF.
Detecting slow server response is there a benchmark I can get from anywhere e.g university experiments data etc.