The delays in granting accounts have other effects on Debian as a whole, besides possibly dissuading people from joining.
The constant stream of sponsoring requests from people who are stuck in the final stages of NM are impeding sponsoring generally. DM is not a complete solution because a lot of these uploads are QA uploads - very useful they are too. It's just that there is no good reason why the nearly-DD's preparing the QA upload should even need a sponsor when the only thing preventing them making the upload themselves is a bottleneck in Debian that hasn't changed or improved in what seems like years.
Personally, I don't see evidence of people being dissuaded from joining - I've advocated a couple of new people recently and I know a few more who are prepared to do what is necessary to become a DD. However, I do not think it is right that existing DDs are expected to sponsor uploads from people who have passed all the hurdles of NM and are simply waiting for another DD to do an administrative task.
To echo Lucas, Debian cannot afford to impede recruitment. Debian also cannot afford to distract the existing manpower with increasing amounts of "workarounds" that fail to fix the problem.
Creating the accounts for new NMs should be considered in a similar manner to an RC bug - if the regular DD cannot find time to do it within a particular timeframe, then the task must be opened up to others who have the time to get it done. With RC bugs, we have NMUs. With NM, we need assistants to be given whatever access is necessary to step in and prevent backlogs.