why didn't sansa tell jon about littlefinger and the knights of the vale. seemed kinda important.
Because that would have ruined the surprise for Jon (and us). Basically one of those completely nonsensical things necessary for the story.
Jon charging the entire Bolton army was likewise pretty dumb. As was "digging trenches" - in frozen ground.
Other than those things, solid episode. That long-shot battle sequence was amazing. Ramsey's end was satisfying. I was hoping there was going to be more to the Umber/Rickon thing, but I guess not.
Oh, and Davos found the stag. I guess that's the end of Mel....