If main characters being in "danger" is all it takes to make something suspenseful, then yeah I guess it was suspenseful. I was just waiting on a deus ex machina to bail them all out like the white walker battle in Beyond the Wall. This time, it was Arya instead of Dany. Technically, Arya is not a deus ex machina because an attempt was made to foreshadow her attack, but she felt that way because of how the rest was handled.
It didn't have to feel rushed or contrived. Her conversation with Melisandre could have been written a little differently, a few seconds could have been spliced in to establish that we should be in suspense waiting for her to show up, there could have been a POV shot of her stalking the Night King that pointed to someone waiting for their moment to strike, etc.
One little change that I would have liked is for her lunge to be shot with the camera facing the other way, heading towards the Night King, so that we can feel the motion of it. The straight-on, over-the-shoulder lunge that we got looks like a cheap special effect. That doesn't change anything about the idea of the scene (which by itself is really good), but it would make it feel better.
Anyway, I'm tired of complaining. I look forward to Sunday's episode being much better.