I disagree.
This chapter was very well executed. The characters' faces and reactions, the timing of the panels, the angles, the explanation of the blink and its use and the sudden rush of everything happening, the dialog, the mystery of what actually happened, everything was very well executed and that's what is effective in creating the sense of tension and awe.
The existence of that sense is not because we don't if the main characters will be ok. That was never in question, so I fail to see why someone would lose that sense just because he remembers that they will ok in the end. The execution of what happens is what makes it.
Now all that remains to be seen is the answer to the mystery of what happened and how it will be resolved, and its certainly possible that it can turn out to be a somewhat disappointing resolution that can retract a bit from this chapter, but it also might not, depending on the execution of the next chapters. But in either of those cases, like I said, I find it certainly better than having the author tiptoeing around this in order to preserve a sense of tension regarding the death of a main character that was never really there in the first place. That would hurt the manga and its style more than a somewhat disappointing resolution for the mystery of this chapter.