HTTP request number of nodes

I have about a dozen NODEMCU's that I use for various measurements. To read them I use HTTP request. Each Nodemcu has a web page that I interrogate for the data and right now I send out a dozen requests at one time. Usually one or two will send back unable to read on each request but it varies over the senors so I get a complete return of data every three read or so. I ping them every 3 seconds. Should I split out the requests over a second or two using a delay node or is one massive request the best way?

give it a go. use a delay node set to "rate limit" mode of around 2 msg per 1 sec.

I noted improvements on a previous job.

Lastly, is there a reason you cannot use MQTT (many ESPxx users do it via MQTT rather than HTTP)?

Was using MQTT at first but for some reason it flooded my network so I changed everything to HTTP. It seemed to work OK. Later on I found out I had some issues with the broker and did get that sorted out but didn't go back to MQTT since HTTP seemed to work.