Mansfield is one of my favourites of all time. 'At the Bay' is gorgeous, and I agree with your assessment that it's more than the sum of its parts, but it's not her best, I don't think. She approaches actual perfection in some of her short stories. I particularly recommend 'The Doll's House' (which contains the characters from 'At the Bay'), 'The Garden Party', and 'Miss Brill'.

Re: Joyce Dubliners has been on my to-read list forever, but for some reason I never actually pick it up to read. I think I will make a point of doing so shortly. I remember reading a short passage from 'The Dead' (you might have posted it, actually) that was amazing.