The Pluspora pod has seen 6,700 members joining, virtually all since 8 October, with numerous others at other pods. I've long had a JoinDiaspora account myself, and revived that.

This compares with 2,900+ members of the G+ Mass Migration community on G+, also since 8 October. (I am one of the mods.) The Change.org petition to retain G+ has seen 31,000+ signatures.

I'd previously conducted assessments of publicly visible G+ posting activity, and arrived at an estimate of 5-10 million such profiles, from a population at the time of about 2.2 billion registered profiles (from a time when Android & Gmail registrations defaulted to registering for G+). Stone Temple Consulting expanded on that research and methodology:

https://www.stonetemple.com/real-numbers-for-the-activity-on...

Google have never been forthcoming with statistics on actual on-G+ activity, though a solid core of single-digit millions, with an extended engagement of 30-120 million, as of March 2015, seems likely.

Other platforms, particularly MeWe, are reporting tens of thousands of new accounts from G+ refugees (Reddit AMA).

https://www.reddit.com/r/IAmA/comments/9sq3jf/im_mark_weinst...

I'm assuming your use of the word "dozens" is a joke, but if not, Diaspora can handle it very well. Their population doubled after Cambridge Analytica hit the news - and within a month or so they lost all those new users: https://nerdpol.ch/posts/e8532ca04b2f013617bf52540061b601

Let's see if they can hold on to the current batch. Diaspora is actually quite usable and stable. I haven't dealt with any issues since I began using it. The docs and non-existent API suck, though.