I do think the suspense has been slightly drawn-out recently, with several pages in some chapters dedicated to military people repeating the countdown, and reiterating Zanka's history with Deido every chapter. I suspect that's a result of the pagecount being so rigid (exactly 18 per chapter) and Fujita's preference for ending chapters on something exciting. Which I can forgive cuz I'm more okay with him taking his time than rushing ahead.
That said, I also think every chapter gives me enough content to be satisfied each week. With the exception of like 1 or 2 chapters before chapter 100, which I do think were slow.
I get what you mean with the mysteries, but the series is winding down, and leaving the reader hanging on a mystery just for the sake of it would be much worse, I think. Also, this is still an action manga at heart, not a mystery manga. Though some chapters deliver way more on the drama than the action, every chapter has *something* to entertain. Whether it's drama, mystery, or action. Sometimes it's impossible to get all at once lol.