Pretty vital, wouldn’t you say? Without it I’m not sure where we’d be at
I mean...yeah?
That would make more sense, but man, what a colossal failure of execution on their part, if that were the case. Your entire plan hinges on Jon (and I guess Dany as well?) staying back, you knew the Wights going up against your army was going to be rough, but that alone enough of a reason to pull you away from your one job that the entire plan rests on?
It's also kind of strange for the plan to revolve around the two dragons being the ones responsible for stopping the Night King, considering that they know that fire doesn't work on them (but is the most effective against the wights), that Dragon Glass/Valerian steel instantly works on them, and that the Night King was the only one who was a threat to the dragons. You would think that they at least should have had an understanding that the two dragons would split duties.
I think that's what Jon's attempted march to the godswood was going for. I don't think Jon believed that the Night King would raise the dead midbattle and Viserion would cut him off. As to Jon joining Dany, I think he was trying to protect her.