I think it's too early to tell, to be completely honest.
I also think the site update doesn't affect most of the readership on tapas. These forums are accessible only to desktop users (or mobile users who for some reason read on the desktop version of the website in a browser on their phone) so of course if you get most of your readers from the forums, you're going to find the update to the site affecting your stats.
My actual comic website has mobile vs desktop analytics and just over 50% of my readerbase on there reads on mobile despite the website not being optimized for mobile use. I'm assuming where tapas has a whole mobile app, my mobile readership on here is much higher. The redesign wouldn't have bothered anyone reading on mobile, therefore most of my readership isn't bothered.
As for a drop in stats, I find every once in a while I have a low week, it happened in mid-February and it happened last week as well. Most of that I attribute to my comic not hitting the trending category, because as soon as it gets high on trending, the new subs pour in. Here are my stats from last month with the highest sub day highlighted, and the three update days I've had this month. As you can see, I got more subs on yesterday's update than I did in on any one day in February, while March 3's update trended much lower than average (which admittedly made me go "oh no it's over" lol).
This got really rambly I'm sorry, the tl;dr is: it's too early to tell, and most of your readership probably has no idea the website changed anyway.