Hi. I've talked to a couple of people who have all had speedy processes, (from Pakistan, so there's atleast some similarity as far as security checks go). As far as I have been able to find out, those applicants whose employment histories are easy to verify have gotten through quickly. Consider the scenario: There's an applicant who has worked for, say 6 organizations - all big multinationals, and his name appears on company websites and online official news/press releases etc in the same capacity that he has mentioned in his application. I assume the first line of security/background checks would be initiated by visa officers online, you know, where linkedin etc profiles come in. So, if all employment history is authenticated through such online checks, and manages to satisfy the visa officer adequately, there would not be any need for detailed background check that takes up time and resources. It holds true in my case, as well as the other few I have talked to. Dr. Ss can shed further light. It makes sense to me, as educational history is already verified through WES, and if there are no grave security/criminal issues, all that remains to be checked is employment history.
Btw, one other thing in common is submitting PCC at the time of application submission, as then I think security/criminal checks can be initiated simultaneously with employment checks.
Hope it makes sense.
Cheers