Many people are focusing on questions, which is always a very low stat on Writing.SE and didn't see much change - there is not much that could possibly change there. Traffic is also popular, but didn't see a lot of change, as most people are still coming in via google.
But according to the site 5k rep analytics the number of votes dropped to around a third (low activity days) to a fifth (high activity days). I think "number of votes" would be a better metric to show how the situation is affecting the core users who are mostly providing answers and voting / editing / flagging / ...
The people that are contributing site views won't know about this. And many prolific askers aren't that active or interested in meta or other things happening on the network. The people mostly answering are the ones that are more likely to participate on meta. Of course there are exceptions to that, but in general that seems to be the trend. At least that's my experience, which is mostly based on WorldBuilding.SE and Writing.SE
I think this query that I found on Interesting queries on Data Explorer could be easier for relevant stats. It gives everyone an overview similar to the 5k / 20k rep "mod tool" site statistics, so that everyone can check every site they are interested in and see how the situation affected the sites you care about.
Here is an example for Writing.SE for the last year; you can see a big spike in march because of a contest to get past 10 questions per day - and a sharp dropoff the last weeks, especially when it comes to votes; normally the "votes / 7 (for scaling)" line is above the "answers" line, now it's below that line: