"for an HTTP Client I just have a simple synchronous JScript wrapper round MSXML2.XMLHTTP"
Yes we do the same. We use TestRail for test case management and access data and post results via the REST apil. We also store stats to mongodb using Sleep.Mongose REST api since there is no TestComplete driver.
I've asked SmartBear to implement a modern http client, but they refuse, saying we should buy "SoapUI" even though it has nothing to do with our usage pattern.
I think a modern http client should now be considered a requirement, it's not just used for testing. I hope they will soon change their stance on this. We should not have to use this ancient ActiveX technology.