Now this may be interesting to see too:

Acording to my data, as of 25/05/2018 we have:
Set 2 (25/05/2018):
      0  Legendary
      8 to Hero (from Sr. Member)
    33 to Sr. Member (from Full Member)
    21 to Full Member (from scratch; two more than on a list I found yesterday with older creation dates), and another additional 53 to Full Member (from  Member) = 74
    1.614 to Member (starting from Jr. Member or below).
-> I'm only listing regular ranks here, since I don't know how the initial Merit played out with Copper Members, VIPs, and so on.

I just went over a post of mine (Which Ranks send sMerit to which Ranks - and who ranked up) with data up to 23/03/2018, and back then I reported:
Set 1 (23/03/2018):
    0  Legendary
    4  Hero Members (from Sr. Member)
   18 Sr. Members (from Full Member)
   39 Full Members (from Member, 3 of them from lower ranks)
 975 Members (from Jr Members or lower)

The comparison is interesting, since it shows the gain in a two month period of time:
Set 2-Set1 (gain in two months):
    0  Legendary
    4  Hero Members (from Sr. Member) -> same
   15 Sr. Members (from Full Member)   -> 16,67% decrease vs Set 1
   35 Full Members (from Member, 3 of them from lower ranks)  -> 10,26% decrease vs Set 1
 639 Members (from Jr Members or lower) -> 34,46% decrease vs Set 1

Since Set1 was derived two months after Merit System Kick-off, the timeframes are all in two month periods.

So as we can see, if we compare results, is that there seems to be a decrease in ranking-up speed as time goes by. This is probably related to the decrease in overall weekly sMerit being awarded, specially compared to the first month.

Thanks, Talk merit. Yes,something like what you mention must be going on in the case I was puzzled by.