While I fully agree with the functionality of the flow that @JuergenAuer has presented (and have used it myself in the past two versions of my own ACME client), there is a significant benefit to be had by triggering and polling one authorization at a time: your user can address any issues with their FQDNs one at a time. This comes at the cost of completion time via serialization of the process. If you trigger all of the authorization checks at once then poll, your client will probably only report any error it encounters for the first invalid authorization it finds. Fixing the cause of that error then submitting a new order sets up a pattern of repeatedly failing authorizations for other FQDNs that also have errors. If there are enough FQDNs in the list with problems, your user will eventually face the limit of 5 invalid authorizations / FQDN / account / hour. The point is: telling Let's Encrypt to check an authorization associated with an FQDN with a known problem that has not been reported to the user yet (and thus likely hasn't been fixed) creates a pattern of waste with consequences.
Please don't tag persons (myself at least) after only three hours. In my opinion that's impatient and rude.
Also I would again urge you to open just a single thread pertaining all your ACME client building efforts. Currently, almost the whole top section of the Client dev section are threads related to a single issue by you: