I don't think this large drop is still caused by the new Merit rules. I'll keep updating this list, because I expect the post count to go up once Bitcoin starts going up in price.
Initially the merit system might have had a significant effect in the drop in posts, as lots of demoted jr members had no reason to keep actively posting in the forum. We were left with those determined to earn merits and those complaining about the unfair system.
The bad market of the past month has reduced interest of most in bitcoin and cryptocurrency related content.
I also expect a rise is activity with that of bitcoin.